https://orcid.org/0000-0003-0220-9249
Figures
Abstract
Background
A year following the onset of the COVID-19 pandemic, new infections and deaths continue to increase in Europe. Serological studies, through providing evidence of past infection, can aid understanding of the population dynamics of SARS-CoV-2 infection.
Objectives
This systematic review of SARS-CoV-2 seroprevalence studies in Europe was undertaken to inform public health strategies including vaccination, that aim to accelerate population immunity.
Methods
We searched the databases Web of Science, MEDLINE, EMBASE, SCOPUS, Cochrane Database of Systematic Reviews and grey literature sources for studies reporting seroprevalence of SARS-CoV-2 antibodies in Europe published between 01/12/2019–30/09/20. We provide a narrative synthesis of included studies. Studies were categorized into subgroups including healthcare workers (HCWs), community, outbreaks, pregnancy and children/school. Due to heterogeneity in other subgroups, we only performed a random effects meta-analysis of the seroprevalence amongst HCWs stratified by their country.
Results
115 studies were included spanning 17 European countries, that estimated the seroprevalence of SARS-CoV-2 from samples obtained between November 2019 –August 2020. A total of 54/115 studies included HCWs with a reported seroprevalence among HCWs ranging from 0.7% to 45.3%, which did not differ significantly by country. In community studies significant heterogeneity was reported in the seroprevalence between different age groups and the majority of studies reported there was no significant difference by gender.
Citation: Vaselli NM, Hungerford D, Shenton B, Khashkhusha A, Cunliffe NA, French N (2021) The seroprevalence of SARS-CoV-2 during the first wave in Europe 2020: A systematic review. PLoS ONE 16(11): e0250541. https://doi.org/10.1371/journal.pone.0250541
Editor: Itamar Ashkenazi, Technion - Israel Institute of Technology, ISRAEL
Received: April 6, 2021; Accepted: September 23, 2021; Published: November 2, 2021
Copyright: © 2021 Vaselli et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the manuscript and its Supporting Information files.
Funding: The authors received no specific funding for this work.
Competing interests: The authors have declared that no competing interests exist.
Introduction
On 11th March 2020 the World Health Organization (WHO) declared the spread of the novel SARS-CoV-2 virus as a pandemic [1]. SARS-CoV-2 is thought to spread mainly by respiratory droplets, airborne transmission and some evidence also suggests spread via fomites [2–4]. SARS-CoV-2 causes varying degrees of illness from mild symptoms including fatigue and myalgia to acute respiratory failure and death [5]. As the pandemic unfolded evidence emerged that a large number of individuals are asymptomatic with SARS-CoV-2 infection [6, 7]. It has been suggested that asymptomatic transmission of SARS-CoV-2 could account for at least a third and up to 59% of transmission across the world [4].
In order to control the spread of SARS-CoV-2 it is important to understand the extent to which different populations have already been exposed to the virus, especially as a large number of infections are asymptomatic and therefore may not have been tested for SARS-CoV-2 at the time of infection. Many countries, organizational bodies and facilities have turned to mass testing to estimate the spread of infection and inform public health measures [8, 9]. One such testing strategy is by nasal and throat swabbing to detect viral RNA which has been piloted in England [10]. A further method is mass testing of the population for antibodies against SARS-CoV-2 [11]. Several tests for immunoglobulin G (IgG), immunoglobulin A(IgA) and immunoglobulin M(IgM) antibodies against SARS-CoV-2 have recently been developed. These broadly include enzyme linked immunosorbent assays, chemiluminescence immunoassays (CLIA) and point of care lateral flow assays [12].
Seroprevalence studies have been used in the past to help with outbreak responses. During a recent Ebola outbreak, seroprevalence studies were performed to gain further information on the immune response and immune protection [13]. Seroprevalence studies have also been used for infections such as rubella, mumps and measles to map resurgence and to gain further information on how public health strategies can target high risk populations [14]. Moreover, seroprevalence studies provide valuable information for vaccination strategies as they help to quantify how much of a population has been exposed to the virus helping to achieve herd immunity and helping to identify populations who may be at greater risk of infection.
By estimating the seroprevalence in different populations we can use the results to understand transmission dynamics, herd immunity and the immune response over time. These studies can help to guide the public health response to ultimately help prevent the spread of SARS-CoV-2. Here we present the results of a systematic review on the seroprevalence of SARS-CoV-2 in Europe.
Methods
Search strategy and selection criteria
This systematic review and meta-analysis adheres to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [15]. The protocol was registered on the University of York database for Prospectively Registered Systematic Reviews (PROSPERO: 2020 CRD42020212149). We systematically searched electronic data sources from (01/12/2019) until (30/09/20) using search terms on seroprevalence and SARS-CoV-2. We searched the following electronic databases: Web of Science, MEDLINE, EMBASE, SCOPUS and Cochrane Database of Systematic Reviews. We also searched database search engine EBSCO to search the following databases: EBSCOhost e-book collection, biomedical reference collection, CINAHL plus and MEDLINE Complete. We conducted a secondary search by searching the reference lists of included studies for relevant articles.
Furthermore, we searched the grey literature. Firstly, we searched pre-print articles in the electronic database search engine EPMC to search pre-print databases including MedRXIV and BioRXIV. Secondly, we then used the database OpenGrey to search research reports, doctoral dissertations, conference papers and other forms of grey literature. Thirdly we searched the websites of national and international health agencies for reports relating to the seroprevalence of SARS-CoV-2 (World Health Organization, European Centres for Disease Control, Public Health England, Department of Health and Social Care in UK). Finally, we conducted a google search for further government reports.
Search terms were developed alongside a health science librarian (Table 1).
Studies were included if they were written in English and published between 1/12/19–30/09/20 and were cross-sectional or cohort studies conducted in Europe. We defined European countries as those listed on the WHO regional office for Europe website [16]. Vaccine evaluations and randomised controlled trials were excluded.
Data extraction
Titles and abstracts of retrieved studies were de-duplicated and screened independently by two reviewers to identify if they met the inclusion criteria. Screened references then underwent full text review by two reviewers independently. Any disagreement between them over the eligibility of studies was resolved through discussion with a third reviewer.
A standardised data extraction form was used. Data was extracted on the characteristics of the study (country, date, setting, selection method, funder), antibody assay employed, specificity and sensitivity of the assay, sample characteristics (age, gender, ethnicity, co-morbidities) and prevalence. Data extraction was carried out autonomously by the reviewers and consensus was sought between the team. Data was recorded on the type of funding the studies received; this included government funding, research grants with some studies receiving no external funding.
Assessment of the methodological quality of included studies
We assessed the risk of bias using an adapted version of the Hoy et al modified Risk of Bias Tool, as used by Nguyen et al [17, 18]. This is a tool designed to assess the risk of bias in population-based prevalence studies. It uses a scoring system to assess the external and internal validity of the study. Studies that score 0–3 points are classified as low risk, 4–6 medium risk and 7–9 high risk. Two reviewers independently applied the criteria. Disagreements were resolved through discussion. After reviewing the relevant literature, we did not perform traditional asymmetry tests and funnel plots for assessing publication bias, as the meta-analysis we conducted was a summary of proportions and not a comparison of treatments/interventions [19, 20].
Data analysis
We provide a narrative synthesis of the findings of all included studies, study population characteristics, antibody assays used and seroprevalence estimates for each study. A narrative synthesis aims to summarise the findings of multiple studies in the form of words and text [21]. Studies were categorized into subgroups including those that examined health care workers (HCWs), community studies, outbreaks, seroprevalence in children/schools and seroprevalence studies performed in pregnant women. We included studies in the subgroup outbreak if they investigated the seroprevalence following a sudden increase in SARS-CoV-2 cases related to time and place in a particular population [22]. We used Metaprop in STATA version 14, statistical software (Stata Corp. College Station, TX, USA), package to perform a random–effects meta-analysis of seroprevalence amongst health care workers (HCWs) stratified by country. The random effect model used the DerSimonian and Laird method with study heterogeneity estimated from the inverse-variance fixed-effect model. The pooled effect estimate was calculated after Freeman-Tukey Double Arcsine Transformation and Wilson score 95% confidence intervals were calculated for individual studies. We also performed a random-effects meta-analysis of seroprevalence amongst health care workers (HCWs) stratified by their risk of exposure to SARS-CoV-2 infected patients. HCWs were categorised as high risk if they worked with patients with known SARS-CoV-2 infection, medium risk if they had patient contact but without known SARS-CoV-2 infection and low risk if they had no patient contact (e.g., laboratory staff and administrative staff). If studies included participants from a mixture of risk groups they were categorised as medium risk. Heterogeneity was measured using the I2 statistic which describes the percentage of total variation due to inter-study heterogeneity. Tests of heterogeneity were undertaken within the sub-groups and for the overall meta-analysis. Sensitivity analysis was done by removing those studies with a moderate risk of bias score. This had no effect of the I2 value, so these studies were included in the final meta-analysis.
Results
The literature search yielded 2126 articles. After removing duplicates and excluding studies based on their abstract or through full text examination 115 studies were identified as eligible (Fig 1). The 115 articles spanned 17 countries in Europe and estimated the seroprevalence of SARS-CoV-2 from serum samples dated from November 2019 –August 2020. The 115 articles reviewed the seroprevalence in approximately 516,361 samples; among included studies 59.92% of subjects were females and the overall age range of participants was 0–90+ years (Table 2).
Assessment of the methodological quality of included studies
Each study underwent a risk of bias assessment using the modified Hoy et al risk of bias tool [18]. Twenty nine of the 115 studies were deemed to be at moderate risk of bias [31, 34, 42, 44, 47, 54, 56, 57, 67, 69, 73, 74, 88, 95, 97, 100, 107, 108, 111, 116, 118, 121, 122, 125, 127, 128, 132, 134, 136]. This was often due to lack of information about the sampling frame, selection process and non-response bias. No studies scored high risk (Table 3).
Results by population subgroups
Health care workers.
54 studies included seroprevalence data among HCWs. These studies included data from 13 countries in Europe and were conducted between February 2020 and August 2020.
The lowest seroprevalence was seen in a teaching hospital in Rome, Italy during the months of March–April 2020, reporting a seroprevalence of 0.7% based on IgG antibodies and 0% based on IgM [77]. The highest seroprevalence (45.3%) was reported in March–April 2020 in a University Hospital in London [119]. Fig 2A shows the seroprevalence of HCWs by country over time. The majority of studies report a seroprevalence < 10% between March–August 2020. A few studies predominately based in the UK report a seroprevalence 20–45% among HCWs during this time period [26, 96, 119, 120, 123, 128, 129, 133].
(A): the seroprevalence of HCWs by country over time. (B): the seroprevalence of HCWs over time stratified by risk group. (C): the seroprevalence of community studies over time by country. (D): the seroprevalence of outbreak studies over time stratified by country and subgroup.
Fig 2B shows the seroprevalence of HCWs categorised by their risk of exposure to SARS-CoV-2 patients over time. All subgroups with a seroprevalence of >30% belonged to either medium or high risk. The majority (67/79) of the subgroups had a seroprevalence of less than 20% regardless of their risk.
There was no significant difference in seroprevalence amongst HCWs when stratified by country (Fig 3). There is a large amount of heterogeneity between the studies (I2 value = 99.27%, p = 0.00). There was no reduction in heterogeneity when moderate risk of bias studies were removed. Similarly, when the seroprevalence amongst HCWs was stratified by their risk of exposure to SARS-CoV-2 patients there was no significant difference (S1 Fig).
Community studies.
In total 34 studies were set in the community, spanning 13 countries. The studies collected data between February 2020—August 2020. Ten of these studies collected samples from blood donors; five studies used residual serum samples from clinics, laboratories and hospital facilities; one study used tissues samples and the remaining studies were randomised population-based studies.
The overall lowest seroprevalence was reported in Greece in March 2020 of 0.24% (0.03–0.45%) [67]. The same study reported an increase in seroprevalence in April of 0.42% (0.23–0.61%). The overall highest seroprevalence was reported in Lodi, Italy during the months of March and April at 23% [76]. The majority of studies reported an overall seroprevalence of less than 10% during the months of February–August 2020 (Fig 2C).
Age. Many of the community studies report the seroprevalence among different age groups. There is significant heterogeneity between the results. In general, lower seroprevalences were reported at the extremes of age. Several studies report a higher seroprevalence among the over 50 age group [40, 52, 74, 85, 86, 104]. In contrast some studies report a higher seroprevalence in the less than 30 years age group, these include studies from Switzerland, the Netherlands, Denmark, France, Luxembourg and the UK [45, 90, 91, 115, 131, 137].
Gender. In the majority of community studies there was no significant difference identified by gender. However, two studies reported a significantly higher number of female participants having antibodies against SARS-CoV-2 [45, 74]. Carrat et al investigated the seroprevalence in three administrative regions of France Ile-de-France (IDF), Grand Est (GE) and Nouvelle-Aquitaine (NA), and reported a significant association of antibodies associated with the female gender only in Nouvelle-Aquitaine [45]. Similarly, Vena et al report a significantly higher seroprevalence among female participants in five administrative regions in Italy [74].
Blood donors. Many studies report the seroprevalence in blood donors as they are usually healthy individuals who represent the general population. There was a large variation in seroprevalence among blood donors between countries and over time.
The lowest seroprevalence in blood donors was reported in Germany between March and June 2020 of 0.91% (0.58–1.24%) [53]. In contrast Percivalle et al reported the highest seroprevalence amongst Italian blood donors in April, living in the Lodi Red Zone of 23.3% [76]. The Lombardi Red Zone is an area of 10 municipalities that were put in total social and commercial lockdown from the 23rd February 2020 [76].The same study reports a seroprevalence of 1.67% in February 2020. In addition a study in the South East of Italy reports a seroprevalence on 0.99% in May 2020 [85].
Similar variations of estimates of seroprevalence were reported in blood donors in the UK. A study conducted in Scotland reported a seroprevalence of 3.17% between the months of March–May 2020 [118]. A seroprevalence of 8.5% (6.9–10%) was reported in blood donors across England in May [132].
Children/ Schools. Seven studies investigated the seroprevalence in school/university settings or among children only, across 5 different countries [49, 64, 69, 116, 121, 136]. Four of the studies examined the seroprevalence in schools [49, 64, 116, 136]. The lowest seroprevalence was reported in Germany; 0.6% among students in grade 8–11 and their teachers in 13 secondary schools in eastern Saxony between the months of May–June 2020 [64]. The highest seroprevalence of 11.7% was reported in students and teachers across schools in England between June-July 2020 (10.5–13.3%) [136].
Fontanet et al investigate the seroprevalence in a high school following an outbreak [44]. They report an overall seroprevalence of 25.86% among pupils, staff and parents of high school pupils [44]. Following the original outbreak Fontanet et al then investigated the seroprevalence among pupils and teachers in primary schools in the local area and reported an overall seroprevalence of 10.4% [49]. They noted that 41.4% of infected children had asymptomatic infection compared to 9.9% of seropositive adults [49].
One study examined the seroprevalence among university students and staff in Greece [69]. They reported an overall seroprevalence of 1%, with no significant difference by age, gender, school or position [69].
Outbreaks. Eight studies across four countries investigated the seroprevalence following an outbreak of SARS-CoV2 [24, 43, 44, 49, 58, 62, 130, 134]. Two of the studies were conducted in the UK and reported a high prevalence of antibodies against SARS-CoV-2 in residents and staff in care homes/nursing homes where there had been a recent SARS-CoV-2 outbreak [130, 134]. They report a high prevalence of antibodies against SARS-CoV-2. Ladhani et al estimated a seroprevalence of 77.9% (73.6–81.7%) and Nsn et al report a seroprevalence of 71.8% [130, 134].
Four studies report seroprevalences following outbreaks among blood donors or communities [24, 43, 58, 62]. They report much lower rates of seroprevalence compared to nursing home outbreaks. Grzelak et al investigated the seroprevalence of pauci-symptomatic individuals in Crepy-en-Valois France and blood donors in the surrounding region following an outbreak; they reported a seroprevalence of 3% in blood donors and 32% in the pauci-symptomatic individuals [43]. Similarly, studies in Germany following community outbreaks report low rates of seroprevalence among residents. Streeck et al reported a prevalence of SARS-CoV-2 antibodies of 13.6% and Weis et al reported a seroprevalence of 8.4% [58, 62]. Fig 2D shows the seroprevalence of these outbreak studies over time.
Pregnancy.
Four studies examined the seroprevalence of SARS-CoV-2 in pregnant women [37, 50, 83, 97]. Two of these studies conducted in Italy between April–June 2020 reported a prevalence of SARS-CoV-2 antibodies of 10.1% and 14.3% in pregnant women in their first trimester screening or at delivery [83, 97]. Mattern et al estimated a seroprevalence of 8% among pregnant women admitted to the delivery room in France in May 2020 [50]. Mattern et al found that the seroprevalence among pregnant women was similar to that of the general public [50].
Egerup et al investigate the seroprevalence among pregnant women, their partners and newborn babies [37]. They report a seroprevalence of 2.85% among parturient women, 3.8% among partners and 1.4% among newborn babies [37]. They report no association between COVID-19 and obstetric or neonatal complications [37].
Assays.
In total 47 different commercial assays and 22 in-house assays were used. The majority of studies used more than one assay. Of the commercial assays 11 were enzyme-linked immunosorbent assay (ELISA), seven were chemiluminescent microparticle immunoassays, two were based on flow cytometry and 27 were point of care tests (POC). The most used commercial assay was the SARS-CoV-2 (IgA/IgG) ELISA EUROIMMUN Medizinische Labordiagnostik, Lübeck, Germany (Table in S2 Table).
Discussion
Our systematic review demonstrates a large variation in the seroprevalence of SARS-CoV-2 antibodies throughout Europe in the first half of 2020.
HCWs in the UK had a much higher seroprevalence compared to HCWs in the rest of Europe during the months of March and August 2020. There are nine studies which took place in UK and six of them reported a seroprevalence of more 20% among HCWs [119, 120, 123, 128, 129, 133]. In contrast, Italy reports a low seroprevalence among HCWs. Of 10 studies among HCWs in Italy, nine reported a seroprevalence of SARS-CoV-2 antibodies of less than 10% [71, 77–82, 87, 88]. Both countries included studies from a mixture of high, medium and low risk HCWs and during this time both countries had high numbers of SARS-CoV-2 infections.
In health care settings, the risk of HCWs of SARS CoV-2 exposure was determined by the COVID-19 caseload coming though the facility and the application of infection control measures. Infection control practices in relation to personal protective equipment (PPE) may in part explain some of the differences.
Between European countries there are differences in the recommended PPE. The UK government guidelines on PPE include the use of eye/face protection, filtering facepiece class 3 (FFP3) respirator, disposable fluid-repellent coverall, and disposable gloves for aerosol-generating procedures and higher-risk acute care areas. For all inpatient ward settings eye/face protection, fluid-resistant (type IIR) surgical mask (FRSM), disposable plastic apron and disposable gloves are recommended [138].
In comparison, the National Institute of Health in Italy recommended that all HCWs wear a full-length gown with long sleeves, hairnet, goggles, gloves and surgical mask in the case of low-risk patients, and hairnet, googles or face-shield, FFP3 mask, water-resistant gown with long sleeves, and two pairs of gloves (second one covering the wrist of gown sleeves) for high risk patients and SARS-CoV-2 positive patients [77].
The main difference in the PPE provided in both countries was that Italy recommended that for all HCWs a full-length gown should be worn, a hairnet and an FFP3 mask when caring for all high-risk patients and all SARS-CoV-2 positive patients. As evidence now supports aerosol spread of SARS-CoV-2, reviews have been conducted investigating the protectiveness of surgical face masks and FFP3 masks. One such study concluded that surgical face masks provide no protection against aerosol particles, in comparison FFP3 masks provided adequate protection [139].
Although the availability and differences in PPE across European countries may partly explain the difference in seroprevalence seen in HCWs, there are other factors that require consideration. For example, differences in public health strategies and the time of their implementation such as the public wearing face masks, closure of educational settings and other public facilities. Furthermore, differences in adherence to infection control measures such as hand hygiene and social distancing could also explain the difference in seroprevalence seen among HCWs across Europe.
Our systematic review found that in the majority of studies in Europe there was no difference in seroprevalence between female and male participants. Our findings are in keeping with a meta-analysis which showed there was no difference in the proportion of males and females with confirmed COVID-19 [140].
Throughout the current pandemic there has been debate on the role of children in the transmission of SARS-CoV-2 and the need for school closure to slow the pandemic. In this review three studies were conducted in schools not involved in an outbreak of SARS-CoV-2. A study in Germany reported the lowest seroprevalence among students and teachers in a school of 0.6% considered by the authors to be in keeping with local surveillance data of the surrounding community [64]. Ulyte et al reported that seroprevalence is inversely related to age in their school study [116]. They conclude this could be due to the lack of social distancing among young children and differences in immune response [116]. In contrast Ladhani et al reported no significant difference between the seroprevalence in students compared to staff [136]. However all studies concluded that there was no major transmission in schools and that the majority of children were asymptomatic or had mild symptoms [64, 116, 136].
However, since these studies have been conducted there has been the introduction of the SARS-CoV-2 variants; B 1.1.7 and B 1.617.2. An increase in these variants have been seen among children and young adolescents with outbreaks occurring in schools and child-care facilities [141, 142].
As new variants emerge it would be reasonable for more school-based studies investigating the seroprevalence among staff and students to be conducted to fully understand transmission dynamics and immune response over time. Viewed within the context of local community data this will help to inform public health strategies to both protect children and to minimise transmission in the wider community.
In studies conducted during local outbreaks, there was a noticeable difference between those conducted in care/nursing homes compared to community and school settings. Those that took place in care/ nursing homes reported a seroprevalence as high as 77.9%, whereas those in a community setting reported a seroprevalence ranging from 3% - 42.4% and those in a school reported a seroprevalence between 10.4% and 25.86% [24, 43, 44, 49, 58, 62, 130] This large discrepancy could be attributable to the close proximity of care/nursing home residents, shared living spaces and the intimate care and handling of residents by staff.
Limitations
This systematic review and meta-analysis had several limitations. Firstly, of the 115 studies included in this review, not all of them could be included in sub-analysis as complete data sets could not be retrieved from every study and data quality was heterogeneous. As this review only included studies performed in Europe, the results of this review can only be applied to European countries. By only including papers written in English we may have overlooked important seroprevalence studies conducted in Europe but published in another language. In addition, most studies were performed either in the UK, Italy, Spain or Germany. There was a large gap in studies being performed in Eastern European countries. Those studies performed in the UK predominately took place in the South of England. Therefore, our review maybe bias towards countries and regions where there is more funding and resources available to conduct seroprevalence studies. In this review the studies used a variety of different assays, with different sensitivities and specificities which could lead to an under or overestimation of the true prevalence reported. Furthermore, many of the studies were pre-print articles that had not undergone peer-review; however, study quality was assessed and subgroup analysis based on risk of bias was performed.
Conclusion
This systematic review and metanalysis highlights substantial heterogeneity between countries, within countries, among professions, and among settings. This heterogeneity, in addition to indicating the general trajectory of the pandemic in different regions, might have been driven by a variety of other factors including governmental policies and restrictions, local guidelines and restrictions, availability of PPE, the time period when the study was conducted and serological test performance. Nevertheless, seroprevalence studies yield large amounts of useful, locally relevant information and should be regularly repeated as the pandemic evolves and local guidelines and restrictions change. As testing standardises and new studies are reported they will also help identify different national experiences across Europe and provide a means to distil best pandemic control practices for the future. As mass vaccinations have been launched in many countries seroprevalence studies will be able to provide valuable information on the immune response over time following vaccination and the need for booster vaccinations, help understand if herd immunity has been achieved and identify populations at risk of transmission and therefore need for vaccination. Finally, as new variants of SARS-CoV-2 now emerge, and many countries prepare for future waves it is vital that regular seroprevalence studies are conducted to aid control by informing public health measures.
Supporting information
S1 Table. Breakdown of quality of assessment results.
https://doi.org/10.1371/journal.pone.0250541.s001
(XLSX)
S2 Table. Commercial assays and their specificity and sensitivity according to the manufacturer.
In some cases, the manufacture’s specificity and sensitivity were unable to be found, so evaluation study data was used instead.
https://doi.org/10.1371/journal.pone.0250541.s002
(PDF)
S1 Fig. Forest plot of the seroprevalence among HCWs stratified by risk of exposure to SARS-CoV-2 patients.
https://doi.org/10.1371/journal.pone.0250541.s003
(TIFF)
Acknowledgments
NC and DH are affiliated to the NIHR Health Protection Research Unit (HPRU) in Gastrointestinal Infections at University of Liverpool, in partnership with Public Health England (PHE), in collaboration with University of Warwick. NC and DH are based at The University of Liverpool. NF and DH are affiliated to the NIHR HPRU Emerging and Zoonotic Infections, a partnership between PHE, the University of Liverpool in collaboration with the Liverpool School of Tropical Medicine and the University of Oxford. The views expressed are those of the author(s) and not necessarily those of the NIHR, the Department of Health and Social Care, HPRU or PHE.
References
- 1.
World Health Organization. WHO Director-General’s opening remarks at the media briefing on COVID-19–11 March 2020 [Internet]. [cited 2020 Nov 18]. Available from: https://www.who.int/director-general/speeches/detail/who-director-general-s-opening-remarks-at-the-media-briefing-on-covid-19—11-march-2020
- 2. Kutti-Sridharan G, Vegunta R, Vegunta R, Mohan BP, Rokkam VRP. SARS-CoV2 in Different Body Fluids, Risks of Transmission, and Preventing COVID-19: A Comprehensive Evidence-Based Review. Int J Prev Med [Internet]. 2020 [cited 2020 Nov 18];11:97. Available from: http://www.ncbi.nlm.nih.gov/pubmed/33042494 pmid:33042494
- 3. Anderson EL, Turnham P, Griffin JR, Clarke CC. Consideration of the Aerosol Transmission for COVID-19 and Public Health. Risk Anal [Internet]. 2020 [cited 2020 Nov 18];40(5):902–7. Available from: http://www.ncbi.nlm.nih.gov/pubmed/32356927 pmid:32356927
- 4. Greenhalgh T, Jimenez JL, Prather KA, Tufekci Z, Fisman D, Schooley R. Ten scientific reasons in support of airborne transmission of SARS-CoV-2. Lancet (London, England) [Internet]. 2021 May 1 [cited 2021 Jun 25];397(10285):1603–5. Available from: http://www.ncbi.nlm.nih.gov/pubmed/33865497 pmid:33865497
- 5. Guan W, Ni Z, Hu Y, Liang W, Ou C, He J, et al. Clinical Characteristics of Coronavirus Disease 2019 in China. N Engl J Med [Internet]. 2020 Apr 30 [cited 2020 Nov 18];382(18):1708–20. Available from: http://www.nejm.org/doi/10.1056/NEJMoa2002032 pmid:32109013
- 6. Day M. Covid-19: four fifths of cases are asymptomatic, China figures indicate. BMJ [Internet]. 2020 Apr 2 [cited 2020 Nov 18];369:m1375. Available from: http://www.ncbi.nlm.nih.gov/pubmed/32241884 pmid:32241884
- 7. Zhou J, Tan Y, Li D, He X, Yuan T, Long Y. Observation and analysis of 26 cases of asymptomatic SARS-COV2 infection. J Infect [Internet]. 2020 Jul [cited 2020 Nov 18];81(1):e69–70. Available from: http://www.ncbi.nlm.nih.gov/pubmed/32251687 pmid:32251687
- 8.
European Centre for Disease Prevention and control. Population-wide testing of SARS-CoV-2: country experiences and potential approaches in the EU/EEA and the United Kingdom European Commission request Definition [Internet]. 2020 [cited 2020 Oct 1]. Available from: https://www.ecdc.europa.eu/sites/default/files/documents/covid-19-population-wide-testing-country-experiences.pdf
- 9.
World Health Organization. COVID-19 Strategy Update April 2020 [Internet]. 2020 [cited 2020 Nov 20]. Available from: https://www.who.int/docs/default-source/coronaviruse/covid-strategy-update-14april2020.pdf?sfvrsn=29da3ba0_19
- 10. Iacobucci G. Covid-19: Mass population testing is rolled out in Liverpool. BMJ [Internet]. 2020 Nov 3 [cited 2020 Nov 18];371:m4268. Available from: http://www.ncbi.nlm.nih.gov/pubmed/33144291 pmid:33144291
- 11. Burgess S, Ponsford MJ, Gill D. Are we underestimating seroprevalence of SARS-CoV-2? BMJ [Internet]. 2020 Sep 3 [cited 2020 Nov 18];370:m3364. Available from: http://www.ncbi.nlm.nih.gov/pubmed/32883673 pmid:32883673
- 12. Watson J, Richter A, Deeks J. Testing for SARS-CoV-2 antibodies. BMJ [Internet]. 2020 Sep 8 [cited 2020 Nov 19];370:m3325. Available from: http://www.ncbi.nlm.nih.gov/pubmed/32900692 pmid:32900692
- 13. Mafopa NG, Russo G, Wadoum REG, Iwerima E, Batwala V, Giovanetti M, et al. Seroprevalence of Ebola virus infection in Bombali District, Sierra Leone. J Public Health Africa [Internet]. 2017 Dec 31 [cited 2020 Nov 20];8(2):732. Available from: http://www.ncbi.nlm.nih.gov/pubmed/29456826 pmid:29456826
- 14. Béraud G, Abrams S, Beutels P, Dervaux B, Hens N. Resurgence risk for measles, mumps and rubella in France in 2018 and 2020. Euro Surveill [Internet]. 2018 [cited 2020 Nov 20];23(25). Available from: http://www.ncbi.nlm.nih.gov/pubmed/29945697 pmid:29945697
- 15. Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ [Internet]. 2021 Mar 29 [cited 2021 Jun 24];n71. Available from: https://www.bmj.com/lookup/doi/10.1136/bmj.n71
- 16.
World Health Organization (WHO). European Countries [Internet]. World Health Organisation. World Health Organization; 2021 [cited 2021 Jun 25]. Available from: https://www.euro.who.int/en/countries
- 17. Hoy D, Brooks P, Woolf A, Blyth F, March L, Bain C, et al. Assessing risk of bias in prevalence studies: modification of an existing tool and evidence of interrater agreement. J Clin Epidemiol [Internet]. 2012 Sep [cited 2021 Jul 2];65(9):934–9. Available from: http://www.ncbi.nlm.nih.gov/pubmed/22742910 pmid:22742910
- 18. Nguyen K, Peer N, Mills E, Kengne A. A Meta-Analysis of the Metabolic Syndrome Prevalence in the Global HIV-Infected Population. PLoS One [Internet]. 2016 [cited 2020 Dec 28];11(3). Available from: https://pubmed.ncbi.nlm.nih.gov/27008536/ pmid:27008536
- 19. Wang N. How to Conduct a Meta-Analysis of Proportions in R: A Comprehensive Tutorial [Internet]. 2018 [cited 2021 Mar 30]. Available from: https://www.researchgate.net/publication/325486099_How_to_Conduct_a_Meta-Analysis_of_Proportions_in_R_A_Comprehensive_Tutorial
- 20. Hunter JP, Saratzis A, Sutton AJ, Boucher RH, Sayers RD, Bown MJ. In meta-analyses of proportion studies, funnel plots were found to be an inaccurate method of assessing publication bias. J Clin Epidemiol [Internet]. 2014 Aug 1 [cited 2021 Mar 30];67(8):897–903. Available from: http://www.ncbi.nlm.nih.gov/pubmed/24794697 pmid:24794697
- 21. Popay J, Roberts H, Sowden A, Petticrew M, Arai L, Rodgers M, et al. Guidance on the Conduct of Narrative Synthesis in Systematic Reviews A Product from the ESRC Methods Programme Peninsula Medical School, Universities of Exeter and Plymouth [Internet]. 2006 [cited 2021 Jun 26]. Available from: https://www.lancaster.ac.uk/media/lancaster-university/content-assets/documents/fhm/dhr/chir/NSsynthesisguidanceVersion1-April2006.pdf
- 22.
Reintjes R, Zanuzdana A. Outbreak Investigations. In: Modern Infectious Disease Epidemiology [Internet]. Nature Publishing Group; 2009 [cited 2021 Jun 24]. p. 159–76. Available from: http://link.springer.com/10.1007/978-0-387-93835-6_9
- 23. Orth-Höller D, Eigentler A, Weseslindtner L, Möst J. Antibody kinetics in primary- and secondary-care physicians with mild to moderate SARS-CoV-2 infection. Emerg Microbes Infect [Internet]. 2020;9(1):1692–4. Available from: http://europepmc.org/abstract/MED/32654611 pmid:32654611
- 24. Knabl L, Mitra T, Kimpel J, Roessler A, Volland A, Walser A, et al. High SARS-CoV-2 Seroprevalence in Children and Adults in the Austrian Ski Resort Ischgl. medRxiv [Internet]. 2020 Jan 1;2020.08.20.20178533. Available from: http://medrxiv.org/content/early/2020/08/22/2020.08.20.20178533.abstract
- 25. Fuereder T, Berghoff AS, Heller G, Haslacher H, Perkmann T, Strassl R, et al. SARS-CoV-2 seroprevalence in oncology healthcare professionals and patients with cancer at a tertiary care centre during the COVID-19 pandemic. ESMO open [Internet]. 2020 Sep;5(5). Available from: https://doi.org/10.1136/esmoopen-2020-000889
- 26. Reiter T, Pajenda S, Wagner L, Gaggl M, Atamaniuk J, Holzer B, et al. Covid-19 serology in nephrology health care workers. medRxiv [Internet]. 2020 Jan 1;2020.07.21.20136218. Available from: http://medrxiv.org/content/early/2020/07/26/2020.07.21.20136218.abstract
- 27. Herzog S, De Bie J, Abrams S, Wouters I, Ekinci E, Patteet L, et al. Seroprevalence of IgG antibodies against SARS coronavirus 2 in Belgium: a prospective cross-sectional nationwide study of residual samples. medRxiv [Internet]. 2020 Jan 1;2020.06.08.20125179. Available from: http://medrxiv.org/content/early/2020/07/30/2020.06.08.20125179.abstract
- 28. Berardis S, Verroken A, Vetillart A, Struyf C, Gilbert M, Gruson D, et al. SARS-CoV-2 seroprevalence in a Belgian cohort of patients with cystic fibrosis. J Cyst Fibros [Internet]. 2020 Aug; Available from: https://europepmc.org/articles/PMC7418700
- 29. Steensels D, Oris E, Coninx L, Nuyens D, Delforge ML, Vermeersch P, et al. Hospital-Wide SARS-CoV-2 Antibody Screening in 3056 Staff in a Tertiary Center in Belgium. JAMA—J Am Med Assoc [Internet]. 2020;324(2):195–7. Available from: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85086874531&doi=10.1001%2Fjama.2020.11160&partnerID=40&md5=963394d58512419685c8fb2d69f16e62
- 30. Martin C, Montesinos I, Dauby N, Gilles C, Dahma H, Van Den Wijngaert S, et al. Dynamics of SARS-CoV-2 RT-PCR positivity and seroprevalence among high-risk healthcare workers and hospital staff. J Hosp Infect [Internet]. 2020 [cited 2020 Dec 23];106(1):102. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7316468/ pmid:32593608
- 31. Desombere I, Mortgat L, Duysburgh E. COVID-19 study: 8,4% of Belgian health workers have antibodies to SARS-COV-2 [Internet]. Sciensano press release. 2020. Available from: https://www.sciensano.be/en/press-corner/covid-19-study-84-belgian-health-workers-have-antibodies-sars-cov-2
- 32. Blairon L, Mokrane S, Wilmet A, Dessilly G, Kabamba-Mukadi B, Beukinga I, et al. Large-scale, molecular and serological SARS-CoV-2 screening of healthcare workers in a 4-site public hospital in Belgium after COVID-19 outbreak. J Infect [Internet]. 2020; Available from: http://europepmc.org/abstract/MED/32739485
- 33. Jerković I, Ljubić T, Bašić Ž, Kružić I, Kunac N, Bezić J, et al. SARS-CoV-2 Antibody Seroprevalence in Industry Workers in Split-Dalmatia and Šibenik-Knin County, Croatia. J Occup Environ Med [Internet]. 2020 Sep 8 [cited 2020 Dec 21]; Available from: https://journals.lww.com/10.1097/JOM.0000000000002020
- 34. Vilibic-Cavlek T, Stevanovic V, Tabain I, Betica-Radic L, Sabadi D, Peric L, et al. Severe acute respiratory syndrome coronavirus 2 seroprevalence among personnel in the healthcare facilities of Croatia, 2020. Rev Soc Bras Med Trop [Internet]. 2020;53:e20200458. Available from: https://europepmc.org/articles/PMC7451497 pmid:32876319
- 35. Iversen K, Bundgaard H, Hasselbalch RB, Kristensen JH, Nielsen PB, Pries-Heje M, et al. Risk of COVID-19 in health-care workers in Denmark: an observational cohort study. Lancet Infect Dis [Internet]. 2020 Aug; Available from: https://europepmc.org/articles/PMC7398038 pmid:32758438
- 36. Erikstrup C, Hother CE, Pedersen OBV, Mølbak K, Skov RL, Holm DK, et al. Estimation of SARS-CoV-2 infection fatality rate by real-time antibody screening of blood donors. medRxiv [Internet]. 2020 Jan 1;2020.04.24.20075291. Available from: http://medrxiv.org/content/early/2020/04/28/2020.04.24.20075291.abstract
- 37. Egerup P, Olsen LF, Christiansen A-MH, Westergaard D, Severinsen ER, Hviid KVR, et al. Impact of SARS-CoV-2 antibodies at delivery in women, partners and newborns. medRxiv [Internet]. 2020 Sep 15 [cited 2021 Jun 27];2020.09.14.20191106. Available from: https://www.medrxiv.org/content/10.1101/2020.09.14.20191106v1
- 38. Jespersen S, Mikkelsen S, Greve T, Kaspersen KA, Tolstrup M, Boldsen JK, et al. SARS-CoV-2 seroprevalence survey among 18,000 healthcare and administrative personnel at hospitals, pre-hospital services, and specialist practitioners in the Central Denmark Region. medRxiv [Internet]. 2020 Jan 1;2020.08.10.20171850. Available from: http://medrxiv.org/content/early/2020/08/12/2020.08.10.20171850.abstract
- 39. Laursen J, Petersen J, Didriksen M, Iversen KK, Ullum H. Prevalence of SARS-CoV-2 IgG/IgM antibodies among Danish and Swedish Falck emergency and non-emergency healthcare workers [Internet]. medRxiv; 2020. Available from: http://europepmc.org/abstract/PPR/PPR219363
- 40. Petersen MS, Strom M, Christiansen DH, Fjallsbak JP, Eliasen EH, Johansen M, et al. Seroprevalence of SARS-CoV-2-Specific Antibodies, Faroe Islands. Emerg Infect Dis [Internet]. 2020;26(11). Available from: http://europepmc.org/search?query=(DOI:10.3201/eid2611.202736)
- 41. Germain N, Herwegh S, Hatzfeld AS, Bocket L, Prevost B, Danze PM, et al. Retrospective study of COVID-19 seroprevalence among tissue donors at the onset of the outbreak before implementation of strict lockdown measures in France [Internet]. medRxiv; 2020. Available from: http://europepmc.org/abstract/PPR/PPR213447
- 42. Solodky ML, Galvez C, Russias B, Detourbet P, N’Guyen-Bonin V, Herr A-L, et al. Lower detection rates of SARS-COV2 antibodies in cancer patients versus health care workers after symptomatic COVID-19. Ann Oncol [Internet]. 2020 [cited 2020 Dec 21];31(8):1087. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7252166/ pmid:32360743
- 43. Grzelak L, Temmam S, Planchais C, Demeret C, Tondeur L, Huon C, et al. A comparison of four serological assays for detecting anti-SARS-CoV-2 antibodies in human serum samples from different populations. Sci Transl Med [Internet]. 2020 Aug 17 [cited 2020 Dec 21];12(559). Available from: https://europepmc.org/article/MED/32817357 pmid:32817357
- 44. Fontanet A, Tondeur L, Madec Y, Grant R, Besombes C, Jolly N, et al. Cluster of COVID-19 in northern France: A retrospective closed cohort study. medRxiv [Internet]. 2020 Jan 1;2020.04.18.20071134. Available from: http://medrxiv.org/content/early/2020/04/23/2020.04.18.20071134.abstract
- 45. Carrat F, de Lamballerie X, Rahib D, Blanche H, Lapidus N, Artaud F, et al. Seroprevalence of SARS-CoV-2 among adults in three regions of France following the lockdown and associated risk factors: a multicohort study [Internet]. medRxiv; 2020. Available from: http://europepmc.org/abstract/PPR/PPR215593
- 46. Gallian P, Pastorino B, Morel P, Chiaroni J, Ninove L, de Lamballerie X. Lower prevalence of antibodies neutralizing SARS-CoV-2 in group O French blood donors. Antiviral Res [Internet]. 2020 Sep;181:104880. Available from: https://europepmc.org/articles/PMC7362788 pmid:32679056
- 47. sermet isabelle, temmam sarah, huon christele, behillil sylvie, gadjos vincent, bigot thomas, et al. Prior infection by seasonal coronaviruses does not prevent SARS-CoV-2 infection and associated Multisystem Inflammatory Syndrome in children. medRxiv [Internet]. 2020 Jan 1;2020.06.29.20142596. Available from: http://medrxiv.org/content/early/2020/06/30/2020.06.29.20142596.abstract
- 48. Lisandru C, Nazli A, Shirley M, Jean C, Stéphane P, Helene SM, et al. Seroprevalence of SARS-CoV-2 IgG antibodies, in Corsica (France), April and June 2020. medRxiv [Internet]. 2020 Sep 30 [cited 2021 Jun 27];2020.09.29.20201368. Available from: https://www.medrxiv.org/content/10.1101/2020.09.29.20201368v1
- 49. Fontanet A, Grant R, Tondeur L, Madec Y, Grzelak L, Cailleau I, et al. SARS-CoV-2 infection in primary schools in northern France: A retrospective cohort study in an area of high transmission. medRxiv [Internet]. 2020 Jan 1;2020.06.25.20140178. Available from: http://medrxiv.org/content/early/2020/06/29/2020.06.25.20140178.1.abstract
- 50. Mattern J, Vauloup-Fellous C, Zakaria H, Benachi A, Carrara J, Letourneau A, et al. Post lockdown COVID-19 seroprevalence and circulation at the time of delivery, France. Spradley FT, editor. PLoS One [Internet]. 2020 Oct 15 [cited 2020 Dec 21];15(10):e0240782. Available from: pmid:33057392
- 51. Péré H, Wack M, Védie B, Guinet ND, Najiby KC, Janot L, et al. Sequential SARS-CoV-2 IgG assays as confirmatory strategy to confirm equivocal results: Hospital-wide antibody screening in 3,569 staff health care workers in Paris. J Clin Virol [Internet]. 2020 Sep; Available from: https://europepmc.org/articles/PMC7470734 pmid:32927358
- 52. Simon D, Tascilar K, Krönke G, Kleyer A, Zaiss MM, Heppt F, et al. Patients with immune-mediated inflammatory diseases receiving cytokine inhibitors have low prevalence of SARS-CoV-2 seroconversion. Nat Commun [Internet]. 2020 Jul;11(1):3774. Available from: https://europepmc.org/articles/PMC7382482 pmid:32709909
- 53. Fischer B, Knabbe C, Vollmer T. SARS-CoV-2 IgG seroprevalence in blood donors located in three different federal states, Germany, March to June 2020. Euro Surveill [Internet]. 2020 Jul;25(28). Available from: https://europepmc.org/articles/PMC7376847
- 54. Brandstetter S, Roth S, Harner S, Buntrock‐Döpke H, Toncheva AA, Borchers N, et al. Symptoms and immunoglobulin development in hospital staff exposed to a SARS‐CoV‐2 outbreak. Kalaycı Ö, editor. Pediatr Allergy Immunol [Internet]. 2020 Oct 18 [cited 2020 Dec 21];31(7):841–7. Available from: https://onlinelibrary.wiley.com/doi/10.1111/pai.13278 pmid:32413201
- 55. Brehm TT, Schwinge D, Lampalzer S, Schlicker V, Kuechen J, Thompson M, et al. High effectiveness of multimodal infection control interventions in preventing SARS−CoV−2 infections in healthcare professionals: a prospective longitudinal seroconversion study. medRxiv [Internet]. 2020 Jan 1;2020.07.31.20165936. Available from: http://medrxiv.org/content/early/2020/08/02/2020.07.31.20165936.abstract
- 56. Behrens GMN, Cossmann A, Stankov M V, Witte T, Ernst D, Happle C, et al. Perceived versus proven SARS-CoV-2-specific immune responses in health-care professionals. Infection [Internet]. 2020 Aug;48(4):631–634. Available from: https://europepmc.org/articles/PMC7286418 pmid:32524515
- 57. Korth J, Wilde B, Dolff S, Anastasiou OE, Krawczyk A, Jahn M, et al. SARS-CoV-2-specific antibody detection in healthcare workers in Germany with direct contact to COVID-19 patients. J Clin Virol [Internet]. 2020 Jul;128:104437. Available from: https://europepmc.org/articles/PMC7219425 pmid:32434708
- 58. Streeck H, Schulte B, Kuemmerer B, Richter E, Hoeller T, Fuhrmann C, et al. Infection fatality rate of SARS-CoV-2 infection in a German community with a super-spreading event. medRxiv [Internet]. 2020 Jan 1;2020.05.04.20090076. Available from: http://medrxiv.org/content/early/2020/06/02/2020.05.04.20090076.abstract
- 59. Krähling V, Kern M, Halwe S, Müller H, Rohde C, Savini M, et al. Title: Epidemiological study to detect active SARS-CoV-2 infections and seropositive persons in a selected cohort of employees in the Frankfurt am Main metropolitan area. [cited 2020 Dec 21]; Available from: https://doi.org/10.1101/2020.05.20.20107730
- 60. Schmidt SB, Grüter L, Boltzmann M, Rollnik JD. Prevalence of serum IgG antibodies against SARS-CoV-2 among clinic staff. Adrish M, editor. PLoS One [Internet]. 2020 Jun 25 [cited 2020 Dec 21];15(6):e0235417. Available from: https://dx.plos.org/10.1371/journal.pone.0235417 pmid:32584894
- 61. Aziz A, Corman V, Echterhoff AKC, Richter A, Schmandke A, Schmidt ML, et al. Seroprevalence and correlates of SARS-CoV-2 neutralizing antibodies: Results from a population-based study in Bonn, Germany [Internet]. medRxiv; 2020. Available from: https://doi.org/10.1101/2020.08.24.20181206
- 62. Weis S, Scherag A, Baier M, Kiehntopf M, Kamradt T, Kolanos S, et al. Seroprevalence of SARS-CoV-2 antibodies in an entirely PCR-sampled and quarantined community after a COVID-19 outbreak—the CoNAN study. medRxiv [Internet]. 2020 Jan 1;2020.07.15.20154112. Available from: http://medrxiv.org/content/early/2020/07/17/2020.07.15.20154112.abstract
- 63. Bahrs C, Kimmig A, Weis S, Ankert J, Hagel S, Maschmann J, et al. Seroprevalence of SARS CoV-2 antibodies in healthcare workers and administration employees: a prospective surveillance study at a 1,400-bed university hospital in Germany. medRxiv [Internet]. 2020 Sep 29 [cited 2021 Jun 26];2020.09.29.20203737. Available from: https://www.medrxiv.org/content/10.1101/2020.09.29.20203737v1
- 64. Armann JP, Unrath M, Kirsten C, Lueck C, Dalpke A, Berner R. Anti-SARS-CoV-2 IgG antibodies in adolescent students and their teachers in Saxony, Germany (SchoolCoviDD19): very low seropraevalence and transmission rates. medRxiv [Internet]. 2020 Jan 1;2020.07.16.20155143. Available from: http://medrxiv.org/content/early/2020/07/28/2020.07.16.20155143.abstract
- 65. Epstude J, Harsch IA. Seroprevalence of COVID-19 antibodies in the cleaning and oncological staff of a municipal clinic. GMS Hyg Infect Control [Internet]. 2020;15:Doc18. Available from: https://europepmc.org/articles/PMC7376972 pmid:32733782
- 66. Hoffmann S, Spallek J, Gremmels H-D, Schiebel J, Hufert F. Testing the backbone of the healthcare system: a prospective serological-epidemiological cohort study of healthcare workers in rural Germany [Internet]. Research Square; 2020. Available from: http://europepmc.org/abstract/PPR/PPR220081
- 67. Bogogiannidou Z, Vontas A, Dadouli K, Kyritsi MA, Soteriades S, Nikoulis DJ, et al. Repeated leftover serosurvey of SARS-CoV-2 IgG antibodies, Greece, March and April 2020. Euro Surveill [Internet]. 2020 Aug;25(31). Available from: https://europepmc.org/articles/PMC7459271
- 68. Psichogiou M, Karabinis A, Pavlopoulou ID, Basoulis D, Petsios K, Roussos S, et al. Antibodies against SARS-CoV-2 among health care workers in a country with low burden of COVID-19. medRxiv [Internet]. 2020 Jan 1;2020.06.23.20137620. Available from: http://medrxiv.org/content/early/2020/06/23/2020.06.23.20137620.abstract
- 69. Tsitsilonis OE, Paraskevis D, Lianidou E, Pierros V, Akalestos A, Kastritis E, et al. Seroprevalence of antibodies against SARS-CoV-2 among the personnel and students of the national and kapodistrian university of athens, greece: A preliminary report. Life [Internet]. 2020;10(9):1–8. Available from: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85091318842&doi=10.3390%2Flife10090214&partnerID=40&md5=3d9928b21aede787d8edb6606006e92a pmid:32967110
- 70. Gudbjartsson DF, Norddahl GL, Melsted P, Gunnarsdottir K, Holm H, Eythorsson E, et al. Humoral Immune Response to SARS-CoV-2 in Iceland. N Engl J Med [Internet]. 2020; Available from: http://europepmc.org/abstract/PMC/PMC7494247 pmid:32871063
- 71. Plebani Padoan, Fedeli Schievano, Vecchiato Lippi, et al. SARS-CoV-2 serosurvey in health care workers of the Veneto Region. Clin Chem Lab Med [Internet]. 2020 [cited 2021 Jan 1];58(12). Available from: https://pubmed.ncbi.nlm.nih.gov/32845861/ pmid:32845861
- 72. Valenti L, Bergna A, Pelusi S, Facciotti F, Lai A, Tarkowski M, et al. SARS-CoV-2 seroprevalence trends in healthy blood donors during the COVID-19 Milan outbreak. medRxiv [Internet]. 2020 Jan 1;2020.05.11.20098442. Available from: http://medrxiv.org/content/early/2020/05/31/2020.05.11.20098442.abstract
- 73. Pancrazzi A, Magliocca P, Lorubbio M, Vaggelli G, Galano A, Mafucci M, et al. Comparison of serologic and molecular SARS-CoV 2 results in a large cohort in Southern Tuscany demonstrates a role for serologic testing to increase diagnostic sensitivity. Clin Biochem [Internet]. 2020;84:87–92. Available from: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85088807240&doi=10.1016%2Fj.clinbiochem.2020.07.002&partnerID=40&md5=fdf2066950d4259b654f1f1c5086359e pmid:32702365
- 74. Vena A, Berruti M, Adessi A, Blumetti P, Brignole M, Colognato R, et al. Prevalence of Antibodies to SARS-CoV-2 in Italian Adults and Associated Risk Factors. J Clin Med [Internet]. 2020 Aug;9(9). Available from: https://doi.org/10.3390/jcm9092780 pmid:32867328
- 75. Norsa L, Cosimo P, Indriolo A, Sansotta N, D’Antiga L, Callegaro A. Asymptomatic SARS-CoV-2 infection in patients with inflammatory bowel disease under biologic treatment. Gastroenterology [Internet]. 2020 Aug; Available from: https://europepmc.org/articles/PMC7448738 pmid:32860790
- 76. Percivalle E, Cambiè G, Cassaniti I, Nepita EV, Maserati R, Ferrari A, et al. Prevalence of SARS-CoV-2 specific neutralising antibodies in blood donors from the Lodi Red Zone in Lombardy, Italy, as at 06 April 2020. Euro Surveill [Internet]. 2020 Jun;25(24). Available from: https://europepmc.org/articles/PMC7315724 pmid:32583766
- 77. Lahner E, Dilaghi E, Prestigiacomo C, Alessio G, Marcellini L, Simmaco M, et al. Prevalence of Sars-Cov-2 Infection in Health Workers (HWs) and Diagnostic Test Performance: The Experience of a Teaching Hospital in Central Italy. Int J Environ Res Public Health [Internet]. 2020 [cited 2020 Dec 20];17(12). Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7345358/
- 78. Fusco FM, Pisaturo M, Iodice V, Bellopede R, Tambaro O, Parrella G, et al. COVID-19 among healthcare workers in a specialist infectious diseases setting in Naples, Southern Italy: results of a cross-sectional surveillance study. J Hosp Infect [Internet]. 2020 Aug;105(4):596–600. Available from: https://europepmc.org/articles/PMC7301109 pmid:32565367
- 79. Sotgiu G, Barassi A, Miozzo M, Saderi L, Piana A, Orfeo N, et al. SARS-CoV-2 specific serological pattern in healthcare workers of an Italian COVID-19 forefront hospital. BMC Pulm Med [Internet]. 2020 Jul;20(1):203. Available from: https://europepmc.org/articles/PMC7388425 pmid:32727446
- 80. Amendola A, Tanzi E, Folgori L, Barcellini L, Bianchi S, Gori M, et al. Low seroprevalence of SARS-CoV-2 infection among healthcare workers of the largest children hospital in Milan during the pandemic wave. Infect Control Hosp Epidemiol [Internet]. 2020 Aug;1–2. Available from: https://europepmc.org/articles/PMC7438626 pmid:32758311
- 81. Carozzi FM, Cusi MG, Pistello M, Galli L, Bartoloni A, Anichini G, et al. Detection of asymptomatic SARS-CoV-2 infections among healthcare workers: results from a large-scale screening program based on rapid serological testing. medRxiv [Internet]. 2020 Jan 1;2020.07.30.20149567. Available from: http://medrxiv.org/content/early/2020/08/04/2020.07.30.20149567.abstract
- 82. Comar M, Brumat M, Concas MP, Argentini G, Bianco A, Bicego L, et al. COVID-19 experience: first Italian survey on healthcare staff members from a Mother-Child Research Hospital using combined molecular and rapid immunoassays test. medRxiv [Internet]. 2020 Apr 22 [cited 2020 Dec 21];2020.04.19.20071563. Available from: https://www.medrxiv.org/content/10.1101/2020.04.19.20071563v1
- 83. Cosma S, Borella F, Carosso A, Sciarrone A, Cusato J, Corcione S, et al. The “scar” of a pandemic: Cumulative incidence of COVID-19 during the first trimester of pregnancy. J Med Virol [Internet]. 2020 Jul; Available from: https://europepmc.org/articles/PMC7361535 pmid:32633869
- 84. Sandri MT, Azzolini E, Torri V, Carloni S, Tedeschi M, Castoldi M, et al. IgG serology in health care and administrative staff populations from 7 hospital representative of different exposures to SARS-CoV-2 in Lombardy, Italy. medRxiv [Internet]. 2020 Jan 1;2020.05.24.20111245. Available from: http://medrxiv.org/content/early/2020/05/26/2020.05.24.20111245.abstract
- 85. Fiore JR, Centra M, De Carlo A, Granato T, Rosa A, Sarno M, et al. Results from a survey in healthy blood donors in South Eastern Italy indicate that we are far away from herd immunity to SARS-CoV-2. J Med Virol [Internet]. 2020 Aug; Available from: https://europepmc.org/articles/PMC7436723 pmid:32790086
- 86. Pagani G, Conti F, Giacomelli A, Bernacchia D, Rondanin R, Prina A, et al. Seroprevalence of SARS-CoV-2 significantly varies with age: Preliminary results from a mass population screening. J Infect [Internet]. 2020 Dec 1 [cited 2020 Dec 21];81(6):e10–2. Available from: https://www.journalofinfection.com/article/S0163-4453(20)30629-0/fulltext pmid:32961253
- 87. Paderno A, Fior M, Berretti G, Schreiber A, Mattavelli D, Deganello A, et al. SARS-CoV-2 infection in healthcare workers: cross-sectional analysis of an Otolaryngology Unit 2 [Internet]. [cited 2020 Dec 21]. Available from: https://www.entnet.org/sites/default/files/uploads/paderno2_sars-cov-2_infection_in_healthcare_workers.pdf
- 88. Tosato F, Pelloso M, Gallo N, Giraudo C, Llanaj G, Cosma C, et al. Severe Acute Respiratory Syndrome Coronavirus 2 Serology in Asymptomatic Healthcare Professionals: Preliminary Experience of a Tertiary Italian Academic Center. medRxiv [Internet]. 2020 Jan 1;2020.04.27.20073858. Available from: http://medrxiv.org/content/early/2020/05/01/2020.04.27.20073858.abstract
- 89. Westerhuis BM, de Bruin E, Chandler FD, Ramakers CRB, Okba NMA, Li W, et al. Homologous and heterologous antibodies to coronavirus 229E, NL63, OC43, HKU1, SARS, MERS and SARS-CoV-2 antigens in an age stratified cross-sectional serosurvey in a large tertiary hospital in The Netherlands. medRxiv [Internet]. 2020 Jan 1;2020.08.21.20177857. Available from: http://medrxiv.org/content/early/2020/08/24/2020.08.21.20177857.abstract
- 90.
Slot E, Hogema B, Reusken CBEM, Reimerink J, Molier M, Karregat JHM, et al. Herd immunity is not a realistic exit strategy during a COVID-19 outbreak [Internet]. Research Square; 2020. Available from: https://doi.org/10.21203/rs.3.rs-25862/v1
- 91. Snoeck CJ, Vaillant M, Abdelrahman T, Satagopam VP, Turner JD, Beaumont K, et al. Prevalence of SARS-CoV-2 infection in the Luxembourgish population: the CON-VINCE study. medRxiv [Internet]. 2020 Jan 1;2020.05.11.20092916. Available from: http://medrxiv.org/content/early/2020/05/18/2020.05.11.20092916.abstract
- 92. Figueiredo-Campos P, Blankenhaus B, Mota C, Gomes A, Serrano M, Ariotti S, et al. Seroprevalence of anti-SARS-CoV-2 antibodies in COVID-19 patients and healthy volunteers [Internet]. medRxiv; 2020. Available from: pmid:33084029
- 93. Dacosta-Urbieta A, Rivero-Calle I, Pardo-Seco J, Redondo-Collazo L, Salas A, Gomez-Rial J, et al. Seroprevalence of SARS-CoV-2 Among Pediatric Healthcare Workers in Spain. Front Pediatr [Internet]. 2020;8. Available from: http://europepmc.org/search?query=(DOI:10.3389/fped.2020.00547) pmid:33042908
- 94. Garcia-Basteiro AL, Moncunill G, Tortajada M, Vidal M, Guinovart C, Jimenez A, et al. Seroprevalence of antibodies against SARS-CoV-2 among health care workers in a large Spanish reference hospital. medRxiv [Internet]. 2020 Jan 1;2020.04.27.20082289. Available from: http://medrxiv.org/content/early/2020/05/02/2020.04.27.20082289.abstract
- 95. Valdivia A, Torres I, Huntley D, Alcaraz MJ, Albert E, de la Asunción C, et al. Caveats in interpreting SARS-CoV-2 IgM+ /IgG- antibody profile in asymptomatic health care workers. J Med Virol [Internet]. 2020 Aug; Available from: https://europepmc.org/articles/PMC7436589
- 96. Galan I, Velasco M, Casas ML, Goyanes MJ, Rodriguez-Caravaca G, Losa JE, et al. SARS-CoV-2 SEROPREVALENCE AMONG ALL WORKERS IN A TEACHING HOSPITAL IN SPAIN: UNMASKING THE RISK. medRxiv [Internet]. 2020 Jan 1;2020.05.29.20116731. Available from: http://medrxiv.org/content/early/2020/05/29/2020.05.29.20116731.abstract
- 97. Crovetto F, Crispi F, Llurba E, Figueras F, Gómez-Roig MD, Gratacós E. Seroprevalence and presentation of SARS-CoV-2 in pregnancy. Lancet [Internet]. 2020;396(10250):530–1. Available from: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85089518432&doi=10.1016%2FS0140-6736%2820%2931714-1&partnerID=40&md5=d1a1beb365755cc3668ff54d05bc525b pmid:32771084
- 98. Garralda Fernandez J, Molero Vilches I, Bermejo Rodriguez A, Cano de Torres I, Colino Romay EI, Garcia-Arata I, et al. Impact of SARS-CoV-2 pandemic among health care workers in a secondary teaching hospital in Spain. medRxiv [Internet]. 2020 Jan 1;2020.07.26.20162529. Available from: http://medrxiv.org/content/early/2020/07/29/2020.07.26.20162529.abstract
- 99. Olalla J, Correa AM, Martin-Escalante MD, Hortas ML, Martin-Sendarrubias MJ, Fuentes V, et al. Search for asymptomatic carriers of SARS-CoV-2 in healthcare workers during the pandemic: a Spanish experience. medRxiv [Internet]. 2020 Jan 1;2020.05.18.20103283. Available from: http://medrxiv.org/content/early/2020/05/20/2020.05.18.20103283.abstract pmid:32777050
- 100. Martín V, Fernández-Villa T, Lamuedra Gil de Gomez M, Mencía-Ares O, Rivero Rodríguez A, Reguero Celada S, et al. Prevalence of SARS-CoV-2 infection in general practitioners and nurses in primary care and nursing homes in the Healthcare Area of León and associated factors. Semergen [Internet]. 2020;46 Suppl 1:35–9. Available from: http://europepmc.org/abstract/MED/32646731 pmid:32646731
- 101. Montenegro P, Brotons C, Fernandez D, Ichazo B, Moral I, Pitarch M, et al. Community seroprevalence of COVID-19 in probable and possible cases at primary health care centres in Spain. Fam Pract [Internet]. 2020; Available from: https://academic.oup.com/fampra/advance-article-pdf/doi/10.1093/fampra/cmaa096/33734322/cmaa096.pdf
- 102. Moncunill G, Mayor A, Santano R, Jimenez A, Vidal M, Tortajada M, et al. SARS-CoV-2 infections and antibody responses among health care workers in a Spanish hospital after a month of follow-up. medRxiv [Internet]. 2020 Jan 1;2020.08.23.20180125. Available from: http://medrxiv.org/content/early/2020/08/25/2020.08.23.20180125.abstract
- 103. Soriano V, Meiriño R, Corral O, Guallar MP. SARS-CoV-2 antibodies in adults in Madrid, Spain. Clin Infect Dis [Internet]. 2020 Jun; Available from: https://europepmc.org/articles/PMC7337724
- 104. Pollán M, Pérez-Gómez B, Pastor-Barriuso R, Oteo J, Hernán MA, Pérez-Olmeda M, et al. Prevalence of SARS-CoV-2 in Spain (ENE-COVID): a nationwide, population-based seroepidemiological study. Lancet (London, England) [Internet]. 2020 Aug;396(10250):535–544. Available from: https://europepmc.org/articles/PMC7336131 pmid:32645347
- 105. Martínez PT. IgG seroprevalence against SARS-CoV-2 in a cohort of 449 non-hospitalized, high-risk exposure individuals. Res Sq [Internet]. 2020 Aug 18 [cited 2021 Jun 27]; Available from: https://www.researchsquare.com/article/rs-53747/v1
- 106. Barallat J, Fernández-Rivas G, Quirant-Sánchez B, Martinez-Caceres , Pina M, Matllo J, et al. Seroprevalence of SARS-CoV-2 IgG Specific Antibodies among Healthcare Workers in the Northern Metropolitan Area of Barcelona, Spain, after the first pandemic wave. [cited 2020 Dec 21]; Available from: pmid:33370363
- 107. Cabezón-Gutiérrez L, Custodio-Cabello S, Palka-Kotlowska M, Oliveros-Acebes E, José García-Navarro M, Khosravi-Shahi P. Seroprevalence of SARS-CoV-2–specific antibodies in cancer outpatients in Madrid (Spain): A single center, prospective, cohort study and a review of available data. Cancer Treat Rev [Internet]. 2020 Sep; Available from: https://europepmc.org/articles/PMC7462449 pmid:32947121
- 108. Castro Dopico X, Hanke L, Sheward DJ, Christian M, Muschiol S, Grinberg NF, et al. Antibody phenotypes and probabilistic seroprevalence estimates during the emergence of SARS-CoV-2 in Sweden. medRxiv [Internet]. 2020 Jan 1;2020.07.17.20155937. Available from: http://medrxiv.org/content/early/2020/08/25/2020.07.17.20155937.abstract
- 109. Rudberg A-S, Havervall S, Manberg A, Jernbom Falk A, Aguilera K, Ng H, et al. SARS-CoV-2 exposure, symptoms and seroprevalence in health care workers. medRxiv [Internet]. 2020 Jan 1;2020.06.22.20137646. Available from: http://medrxiv.org/content/early/2020/06/23/2020.06.22.20137646.abstract
- 110. Lindahl JF, Hoffman T, Esmaeilzadeh M, Olsen B, Winter R, Amer S, et al. High seroprevalence of SARS-CoV-2 in elderly care employees in Sweden [Internet]. Vol. 10, Infection ecology & epidemiology. 2020. p. 1789036. Available from: http://europepmc.org/abstract/MED/32939231 pmid:32939231
- 111. Roxhed N, Bendes A, Dale M, Mattsson C, Hanke L, Dodig-Crnkovic T, et al. A translational multiplex serology approach to profile the prevalence of anti-SARS-CoV-2 antibodies in home-sampled blood. medRxiv [Internet]. 2020 Jan 1;2020.07.01.20143966. Available from: http://medrxiv.org/content/early/2020/07/02/2020.07.01.20143966.abstract
- 112. Lidström A-K, Sund F, Albinsson B, Lindbäck J, Westman G. Work at inpatient care units is associated with an increased risk of SARS-CoV-2 infection; a cross-sectional study of 8679 healthcare workers in Sweden. Ups J Med Sci [Internet]. 2020 Nov [cited 2021 Jun 27];125(4):305–10. Available from: http://www.ncbi.nlm.nih.gov/pubmed/32684119 pmid:32684119
- 113. Lundkvist Å, Hanson S, Olsen B. Pronounced difference in Covid-19 antibody prevalence indicates cluster transmission in Stockholm, Sweden [Internet]. Vol. 10, Infection ecology & epidemiology. 2020. p. 1806505. Available from: http://europepmc.org/abstract/MED/32944166 pmid:32944166
- 114. Emmenegger M, De Cecco E, Lamparter D, Jacquat RPB, Ebner D, Schneider MM, et al. Early peak and rapid decline of SARS-CoV-2 seroprevalence in a Swiss metropolitan region. medRxiv [Internet]. 2020 Jan 1;2020.05.31.20118554. Available from: http://medrxiv.org/content/early/2020/08/07/2020.05.31.20118554.abstract
- 115. Stringhini S, Wisniak A, Piumatti G, Azman AS, Lauer SA, Baysson H, et al. Seroprevalence of anti-SARS-CoV-2 IgG antibodies in Geneva, Switzerland (SEROCoV-POP): a population-based study. Lancet (London, England) [Internet]. 2020 Aug;396(10247):313–319. Available from: https://europepmc.org/articles/PMC7289564 pmid:32534626
- 116. Ulyte A, Radtke T, Abela I, Haile S, Blankenberger J, Jung R, et al. Variation in SARS-CoV-2 seroprevalence in school-children across districts, schools and classes [Internet]. medRxiv; 2020. Available from: http://europepmc.org/abstract/PPR/PPR215541
- 117. ALKURT G , MURT A,AYDIN Z, TATLI O, AGAOGLU NB, IRVEM A, et al. Seroprevalence of Coronavirus Disease 2019 (COVID-19) Among Health Care Workers from Three Pandemic Hospitals of Turkey. medRxiv [Internet]. 2020 Jan 1;2020.08.19.20178095. Available from: http://medrxiv.org/content/early/2020/08/22/2020.08.19.20178095.abstract
- 118. Thompson CP, Grayson N, Paton R, Bolton JS, Lourenço J, Penman B, et al. Detection of neutralising antibodies to SARS coronavirus 2 to determine population exposure in Scottish blood donors between March and May 2020. medRxiv [Internet]. 2020 Jan 1;2020.04.13.20060467. Available from: http://medrxiv.org/content/early/2020/07/29/2020.04.13.20060467.abstract pmid:33094713
- 119. Houlihan C, Vora N, Byrne T, Lewer D, Heaney J, Moore D. SARS-CoV-2 virus and antibodies in front-line Health Care Workers in an acute hospital in London: preliminary results from a longitudinal study. medRxiv. 2020;
- 120. Pallett SJC, Rayment M, Patel A, Fitzgerald-Smith SAM, Denny SJ, Charani E, et al. Point-of-care serological assays for delayed SARS-CoV-2 case identification among health-care workers in the UK: a prospective multicentre cohort study. Lancet Respir Med [Internet]. 2020 Sep;8(9):885–894. Available from: https://europepmc.org/articles/PMC7380925 pmid:32717210
- 121. Waterfield T, Watson C, Moore R, Ferris K, Tonry C, Watt A, et al. Seroprevalence of SARS-CoV-2 antibodies in children: a prospective multicentre cohort study. Arch Dis Child [Internet]. 2020 Nov 23 [cited 2020 Dec 21]; Available from: https://adc.bmj.com/content/early/2020/11/22/archdischild-2020-320558
- 122. Eyre DW, Lumley SF, O'Do nell D, Cam bell M, Sims E, L wson E, et al. Differential occupational risks to healthcare workers from SARS-CoV-2: A prospective observational study. medRxiv [Internet]. 2020 Jan 1;2020.06.24.20135038. Available from: http://medrxiv.org/content/early/2020/06/29/2020.06.24.20135038.1.abstract
- 123. Shields A, Faustini SE, Perez-Toledo M, Jossi S, Aldera E, Allen JD, et al. SARS-CoV-2 seroprevalence and asymptomatic viral carriage in healthcare workers: a cross-sectional study. Thorax [Internet]. 2020 Aug; Available from: https://europepmc.org/articles/PMC7462045 pmid:32917840
- 124. Clarke C, Prendecki M, Dhutia A, Ali MA, Sajjad H, Shivakumar O, et al. High Prevalence of Asymptomatic COVID-19 Infection in Hemodialysis Patients Detected Using Serologic Screening. J Am Soc Nephrol [Internet]. 2020 Sep;31(9):1969–1975. Available from: pmid:32732391
- 125. Wells PM, Doores KJ, Couvreur S, Nunez RM, Seow J, Graham C, et al. Estimates of the rate of infection and asymptomatic COVID-19 disease in a population sample from SE England. J Infect [Internet]. 2020 Dec 1 [cited 2020 Dec 21];81(6):931–6. Available from: https://www.journalofinfection.com/article/S0163-4453(20)30653-8/fulltext pmid:33068628
- 126.
The Government of Jersey. SARS-CoV-2: Prevalence of antibodies in Jersey. Jersey, UK, 2020. [Internet]. 2020 [cited 2020 Dec 21]. Available from: www.gov.je/statistics
- 127. Poulikakos D, Sinha S, Kalra PA. SARS-CoV-2 antibody screening in healthcare workers in a tertiary centre in North West England. J Clin Virol [Internet]. 2020 Aug;129:104545. Available from: https://europepmc.org/articles/PMC7338856 pmid:32659709
- 128. Khalil A, Hill R, Wright A, Ladhani S, O’Brien P. SARS-CoV-2-specific antibody detection in healthcare workers in a UK maternity Hospital: Correlation with SARS-CoV-2 RT-PCR results. Clin Infect Dis [Internet]. 2020 Aug; Available from: https://europepmc.org/articles/PMC7454457
- 129. Grant JJ, Wilmore SMS, McCann NS, Donnelly O, Lai RWL, Kinsella MJ, et al. Seroprevalence of SARS-CoV-2 antibodies in healthcare workers at a London NHS Trust. Infect Control Hosp Epidemiol [Internet]. 2020 Aug;1–3. Available from: https://europepmc.org/articles/PMC7438618
- 130. Ladhani SN, Jeffery-Smith AJ, Patel M, Janarthanan R, Fok J, Crawley-Boevey E, et al. High prevalence of SARS-CoV-2 antibodies in care homes affected by COVID-19; a prospective cohort study in England. medRxiv [Internet]. 2020 Jan 1;2020.08.10.20171413. Available from: http://medrxiv.org/content/early/2020/08/12/2020.08.10.20171413.abstract
- 131.
UK Biobank. UK Biobank SARS-CoV2 Serology Study (Weekly Report—21 July 2020) [Internet]. 2020 [cited 2020 Dec 21]. Available from: https://www.ukbiobank.ac.uk/media/s3af0k5q/ukb_serologystudy_month1_report.pdf
- 132.
Public Health England. Weekly Coronavirus Disease 2019 (COVID-19) Surveillance Report London: PHE; 2020 [Internet]. 2020 [cited 2020 Dec 21]. Available from: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/889981/Weekly_COVID19_Epidemiological_Summary_w23.pdf
- 133. Mulchandani R, Taylor-Phillips S, Jones H, Ades T, Borrow R, Linley E, et al. Self assessment overestimates historical COVID-19 disease relative to sensitive serological assays: cross sectional study in UK key workers. medRxiv [Internet]. 2020 Jan 1;2020.08.19.20178186. Available from: http://medrxiv.org/content/early/2020/08/22/2020.08.19.20178186.abstract
- 134. Nsn G, C J, R M, P R, N L, Sn L, et al. High rates of SARS-CoV-2 seropositivity in nursing home residents. J Infect [Internet]. 2020 Aug; Available from: https://europepmc.org/articles/PMC7449890 pmid:32860817
- 135. Favara D, McAdam K, Cooke A, Bordessa-Kelly A, Budriunaite I, Bossingham S, et al. SARS-CoV-2 antigen and antibody prevalence among UK staff working with cancer patients during the COVID-19 pandemic [Internet]. medRxiv; 2020. Available from: http://europepmc.org/abstract/PPR/PPR217237
- 136. Ladhani S. Prospective active national surveillance of preschools and primary schools for SARS-CoV-2 infection and transmission in England, June 2020 (sKIDs COVID-19 surveillance in school KIDs) [Internet]. 2020 [cited 2020 Dec 21]. Available from: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/914700/sKIDs_Phase1Report_01sep2020.pdf
- 137. Ward H, Atchison CJ, Whitaker M, Ainslie KEC, Elliott J, Okell LC, et al. Antibody prevalence for SARS-CoV-2 in England following first peak of the pandemic: REACT2 study in 100,000 adults. medRxiv [Internet]. 2020 Jan 1;2020.08.12.20173690. Available from: http://medrxiv.org/content/early/2020/08/21/2020.08.12.20173690.abstract
- 138. Mantelakis A, Spiers HVM, Lee CW, Chambers A, Joshi A. Availability of Personal Protective Equipment in NHS Hospitals During COVID-19: A National Survey. Ann Work Expo Heal [Internet]. [cited 2020 Dec 28]; Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7499547/ pmid:32914175
- 139. Douglas JDM, McLean N, Horsley C, Higgins G, Douglas CM, Robertson E. COVID-19: smoke testing of surgical mask and respirators. Occup Med (Lond) [Internet]. 2020 [cited 2021 Jun 26];70(8):556–63. Available from: http://www.ncbi.nlm.nih.gov/pubmed/33150448 pmid:33150448
- 140. Peckham H, de Gruijter NM, Raine C, Radziszewska A, Ciurtin C, Wedderburn LR, et al. Male sex identified by global COVID-19 meta-analysis as a risk factor for death and ITU admission. Nat Commun [Internet]. 2020 Dec 9 [cited 2020 Dec 28];11(1):6317. Available from: http://www.nature.com/articles/s41467-020-19741-6 pmid:33298944
- 141. Gurdasani D, Hisham Z, Reicher S, Mckee M. Covid-19 and the delta variant—we need an urgent focus on mitigations in schools—The BMJ [Internet]. 2021 [cited 2021 Jun 26]. Available from: https://blogs.bmj.com/bmj/2021/06/11/covid-19-and-the-delta-variant-we-need-an-urgent-focus-on-mitigations-in-schools/
- 142. Loenenbach A, Markus I, Lehfeld A-S, An der Heiden M, Haas W, Kiegele M, et al. SARS-CoV-2 variant B.1.1.7 susceptibility and infectiousness of children and adults deduced from investigations of childcare centre outbreaks, Germany, 2021. Euro Surveill [Internet]. 2021 [cited 2021 Jun 26];26(21). Available from: http://www.ncbi.nlm.nih.gov/pubmed/34047274