https://orcid.org/0000-0002-9401-0706
Figures
Abstract
Background
Reporting quality of aromatherapy-focused research in humans is inconsistent and often incomplete yet there are no (North American or American) nationally or internationally agreed upon core criteria for aromatherapy-focused research. The Aromatic Research Quality Appraisal Task Force developed the Transparent Reporting for Essential oil and Aroma Therapeutic Studies (TREATS) checklist as initial steps toward developing a reporting guideline. The purpose of this Delphi study is to engage with an international community of aromatherapy researchers to reach consensus on which items should be included in reports of aromatherapy-focused studies in humans. The result of the consensus process will be to publish an aromatherapy research reporting guideline that can be used as an extension to existing research reporting guidelines for various studies such as randomized controlled trials, observational studies, and case reports.
Methods
A modified Delphi consensus study will be used. The consensus study, approved by the West Virginia University Institutional Review Board, will consist of up to four rounds of an online survey. To improve understanding and buy-in, experts attending a large international aromatherapy-focused conference will take part in a four-hour in-person/virtual hybrid introductory meeting where they can learn the study process and ask questions. The 48-item survey is divided into categories covering study products, processes, aromatherapy intervention, safety, sustainability, and olfactory ability and aroma preference. Participants will be asked to rate each checklist item for relevance on a 5-point Likert scale ranging from “of little importance” to “extremely important”. During the Delphi study, participants can provide comments and, in the first and second rounds, may suggest additional items or modifications to existing items. An item will be automatically included in the final guidelines if it is rated as "very important" or "extremely important" by at least ≥80% of the participants in Rounds 1–3, and automatically excluded if > 50% of participants rate the item as “not important” or “of little importance”. Aggregated ratings will be statistically analyzed for response rates, level of agreement, medians, and interquartile ranges.
Discussion
This protocol supports conducting a Delphi consensus that will add to the current knowledge of items considered necessary for complete and consistent reporting of aromatherapy-focused research in humans. This is of international significance as world-wide use and research of aromatherapy and essential oils in humans has continued to increase, currently without consistent and clear reporting. The Delphi method is appropriate for developing consensus between diverse experts, researchers, and practitioners as it offers anonymity and minimizes bias. Findings will contribute to creating an extension to primary reporting guidelines.
Citation: Reven ME, Bowles EJ, Ablard K, Peppers-Citizen M, May-Fitzgerald A, Joswiak D, et al. (2025) Essential criteria for reporting of aromatherapy-focused research in humans: An international Delphi consensus study protocol. PLoS ONE 20(3): e0318379. https://doi.org/10.1371/journal.pone.0318379
Editor: Muhammad Junaid Farrukh, UCSI University, MALAYSIA
Received: October 5, 2024; Accepted: January 14, 2025; Published: March 24, 2025
Copyright: © 2025 Reven 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: No datasets were generated or analysed during the current study. All relevant data from this study will be made available upon study completion.
Funding: Ruth and Robert Kuhn Nursing Research Fund at West Virginia University. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: I have read the journal’s policy and the authors of this manuscript have the following competing interests: Membership on the board of ARQAT. This does not alter our adherence to PLOS ONE policies on sharing data and materials.
Introduction
There is a growing interest and a large recent increase in the number of published aromatherapy-focused research articles [1, 2]. Several Cochrane systematic reviews on the use of aromatherapy for various health conditions conclude that the majority of aromatherapy research studies are either poorly designed or poorly reported and that it is difficult to draw conclusions about the effects of aromatherapy due to these limitations [3, 4]. This diminishes the potential for use in evidence-informed practice, reproducibility, summary research, policy decisions, and safety guidelines, and does not align with conventional sustainability principles.
As the research interest in essential oils and aromatherapy increases, aromatherapy researchers need to consider the ethics of using essential oils from plants that are facing extinction. At least 18% of plants from which essential oils are sourced are listed as threatened on the International Union for Conservation of Nature (IUCN) Red List [5]. Aromatherapy researchers should demonstrate consideration of environmental ethical issues surrounding essential oil choices for their research.
Many complementary therapies, including aromatherapy, require consideration of factors beyond those usually considered relevant in pharmaceutical drug trials. For example, aromatherapy-focused research should account for the effects of olfactory stimuli on mood, memory, and central nervous system stimulation, and the impact of a person’s previous experience and reflexive responses to essential oils that may bias the results of an aromatherapy trial [5–7].
The Aromatic Research Quality Appraisal Taskforce (ARQAT) formed in 2021 developed and published an aromatherapy research quality appraisal checklist known as TREATS (Transparent Reporting for Essential oil and Aroma Therapeutic Studies) [8]. However, the TREATS was derived from the input of only a few dozen people, mainly from the United States of America, and it is time to consider the TREATS and additional items with a group of international aromatherapy researchers and experts to derive a consensus-based, globally created, Aromatherapy Research Reporting Guideline.
To address this need ARQAT is conducting a Delphi consensus study to determine the minimum necessary items for aromatherapy research reporting. The study participants will include English-speaking aromatherapy-focused researchers, academics, and health care and aromatherapy professionals from around the globe. The study will consist of up to four rounds of surveys delivered electronically. The first two rounds will include qualitative and quantitative data. Data will be analyzed between each round to determine consensus.
Reporting guidelines are simple, structured tools for researchers to use while writing manuscripts. They provide minimum lists of items needed to ensure that research reports can be i) understood by a reader, ii) replicated by a researcher, iii) used by a doctor to make a clinical decision, and iv) included in a systematic review [9].
Materials and methods
Aim
The objective is to conduct an international Delphi consensus study, to create reporting guidelines for aromatherapy-focused research in humans. These guidelines will be used in addition to existing reporting guidelines for various aromatherapy study designs including randomized controlled trials, observational studies, case reports, and other applicable studies. Existing research reporting guidelines are insufficient for prompting adequate reporting of criteria specific to aromatherapy research in humans.
Study design and setting
This study uses a modified Delphi methodology informed by Spranger et al. (2022) whose review outlined important criteria for the conduct of Delphi studies [10]. The traditional Delphi method of having face-to-face meetings will be modified by using an online survey to enable asynchronous completion of the rounds by respondents from different countries. There will be up to four rounds (the fourth used if needed). An initial in-person/hybrid meeting will be conducted during a major aromatherapy conference, allowing potential participants to find out about the study and ask questions.
The study has been designed from a realist perspective, acknowledging that there is likely to be an optimal set of reporting criteria arising from respondents’ personal beliefs and research backgrounds. The use of the modified Delphi methodology allows a robust set of items to be identified across international methods of conducting aromatherapy research. The Delphi technique has been chosen because it allows for anonymity while seeking consensus [10–12]. It is often used to determine consensus on healthcare quality indicators [13, 14].
All identified potential Delphi study participants will be sent an introductory email and Participant Information Sheet (S1 File) that will provide specific details about the project, explain consent for participation, and outline the ability to withdraw at any time. They will be invited to attend the hybrid meeting. After this meeting, all potential participants will be sent an email with the cover letter (S2 File) and a unique link to the survey. Consent to participate will be implied by the completion of the first round of the Delphi survey. Contact with participants will be via email and strategies to ensure retention will include personalized survey invitations and regular reminders. A unique identifier will be assigned to each participant.
Participants
Participants who are proficient in reading and writing English will include representatives from two stakeholder categories: 1) researchers and academics, and 2) aromatherapy and health care professionals. People who meet these criteria will be invited to participate.
Recruitment
Recruitment draws from the global community aiming to include as many countries as possible.
Researchers and academics.
To recruit researchers, a literature review conducted by authors EJB and MER was used to identify authors of systematic reviews of aromatherapy-focused studies published between 2018 and 2023 (Fig 1). This identified 44 reviews whose authors documented concerns about the quality of reporting of at least one aspect of the aromatic portion of the research such as chemical constituents, Latin binomials, and quality control [8]. The authors of these reviews will be invited to join the Delphi study with the proviso that they are proficient in reading and writing English. Additional corresponding authors include those who have published aromatherapy-focused research in peer-reviewed publications available in English between 2018 and 2024 beyond the reviews noted above.
Aromatherapy and health care professionals.
We will contact professional aromatherapy organizations and educational institutions and ask them to invite their members to express their interest. To solicit feedback from the global aromatherapy community we will draw from international organizations including the International Clinical Aromatherapy Network (ICAN) [15], the Alliance of International Aromatherapists (AIA) [16], the National Association for Holistic Aromatherapy (NAHA) [17], the International Federation of Professional Aromatherapists (IFPA) [18], International Federation of Aromatherapists (IFA) [19], the Canadian Alliance of Aromatherapy (CAOA) [20], the Canadian Federation of Aromatherapist (CFA) [21], ABRAROMA (Associação Brasileira de Aromaterapia e Aromatologia) (Brazil) [22], ARTHES (Association of Professional Aromatherapy and Care in Switzerland) (Switzerland) [23], and others.
Snowball recruitment will be used allowing participants to recommend other qualified participants for inclusion in the study. It is hoped that the global community of researchers will participate. The Participant Information Sheet, introductory email, and invitations to participate will be sent. Referrals will be accepted until the official start date of the survey.
Sample size
In a critique of healthcare Delphi studies, Nasa et al., (2021) suggested that 30–50 participants completing the final round should be sufficient numbers for a robust consensus [24]. In a recent Delphi study involving another integrative modality, the CheckList stAndardizing the Reporting of Interventions for Yoga (CLARIFY) Delphi study [25], 25% (32) of the initial 128 participants completed the third round. Our study will aim to recruit at least 150 participants so if a similar drop-out rate is experienced, we can hope to have about 37 participants remaining in the final round.
Criteria for the Delphi participants to consider
The items are based on the TREATS checklist with 10 extra items including two sustainability-focused items contributed by Airmid Institute.
Item and categories
A total of 48 items have been developed and will be assessed in the Delphi rounds. These items are grouped into sections including, 1) title, 2) characterization of essential oil(s)/volatile extract(s), 3) rationale for study design and choice of plant materials, 4) aromatherapist involvement and safe handling of essential oils, 5) topical application methods and dosage regime, 6) inhalation methods and dosage regime, and 7) participant olfactory capacity and experience (Table 1).
Survey format
Up to four rounds of online surveys will be administered using the West Virginia University (WVU) REDCap platform [26, 27]. The online survey has been constructed and pilot tested for comprehension and adequate function of the survey format. Unique links for Round 1 will be emailed to participants on the official starting date. We anticipate Round 1 will be the longest and will ask participants to allow for up to one hour. In Round 1, all participants are asked for demographic information. In subsequent rounds, participants are only asked for first and last names. For subsequent rounds, time required to complete the survey will be closer to 20 to 30 minutes. If a fourth round is needed, it should only take about 5 minutes. It is recommended that 4 to 6 weeks be given between rounds [10] though it may only be two weeks between rounds 2 and 3 and if needed rounds 3 and 4. Changes and updates will be communicated via email. Participants will receive up to five email reminders to complete each round before it closes.
Rating process
Participants will be asked to rate each item on a 5-point Likert scale during each round. Relevance for inclusion means the item is believed to be necessary for minimum clear and complete reporting of aromatherapy research in humans. The Likert scale responses are:
- 1) of no importance,
- 2) of little importance,
- 3) important,
- 4) very important,
- 5) extremely important, and
- 6) not my area of expertise.
Items rated as 6) will not be included in the calculation of items to be included and excluded.
Data handling
All data will be anonymized, aggregated, and shared with participants at the end of each Round. In Rounds 1 and 2, opportunity for comments is provided. Qualitative, free-text comments from Rounds 1 and 2 will be grouped as general comments. If any new items are suggested by participants at the end of Round 1, they will be considered for inclusion in Round 2. In Round 2, participants will be presented with items that did not reach consensus in Round 1 and asked to re-rate these remaining items. Round 2 comments will be accepted but no new items will be added to Round 3. Participants do not have to give the same score as they gave in Round 1 if their opinion has changed. If there are any items that do not reach consensus in Round 2, they will be presented again in Round 3. Round 4 will be used only if consensus remains unattained. Survey responses can be downloaded by participants for reference. An explanatory document is provided to add clarity for items in Round 1 (S3 File).
Consensus criteria.
De-identified participant responses will be analyzed using Statistical Package for the Social Sciences (IBM SPSS) and Microsoft Excel software. Analysis will occur after each survey round and form the content of the subsequent round’s survey. The a priori item consensus criterion for automatic inclusion in the Delphi guidelines will be a rating of ‘Very important’ or ‘Extremely important’ by ≥80% of participants, and the criterion for automatic exclusion will be a rating of ‘Of no importance’ or ‘Of little importance’ by ≥50% of participants. If less than 75% of participants have given scores of ‘Important’, ‘Very important’, or ‘Extremely important’, the item will also be excluded. Items not reaching inclusion or exclusion consensus, but rated as ‘Important’, ‘Very important’ or ‘Extremely important’ by ≥75% participants will be forwarded to the subsequent round for re-rating. As some participants may choose the “Not my area of expertise” response, the number of responses for each item will be taken into account for the calculation of the inclusion/exclusion criteria.
To summarize each round, Likert ratings for each item will be analyzed quantitatively and expressed as a percentage for each of the five Likert categories, together with 25, 50, and 75 percentile scores (median and interquartile range [IQR]).
Termination criteria.
From Round 2, the median and IQR of any items not reaching inclusion or exclusion consensus will be compared with the median and IQR of the previous round. If these scores decrease or remain unchanged between a current and previous round, the item will be excluded; if these scores increase then the item will be forwarded to the subsequent round for re-rating.
Data management plan
Electronic records will be handled and stored per the WVU Data Protection plan. MER is the Principal Investigator (PI) and administrator of the electronic data and the only person able to provide access to these files. Paper documents created for this project, if any, will be stored in a locked filing cabinet in a locked office at WVU. All research data will be stored per WVU Data Protection standards for at least three years and then destroyed in accordance with WVU protocols.
Amendments to this protocol will be handled by updating the protocol in the digital file and alerting research team members via email. Original protocol information will remain intact and changes tracked.
Potential risks and risk management
Potential risks related to this study are considered minimal. Survey participants may feel inconvenienced by the process required in the study. This includes being asked to complete the required reading of the PIS, agree to participate by using the link to begin the first survey, and participate in up to three additional rounds of the survey process. To mitigate these risks, the project scope and aims will be clearly presented. The REDCap system allows participants to stop and save survey responses and return to complete as many times as needed. Additionally, we will provide a comprehensive explanatory document that participants will download and have throughout the process. This will serve to answer possible questions about the meaning of an item and help with context. Finally, participants will be instructed that they can stop participating at any time without fear of repercussions.
Ethical considerations
Consent will be implied when a participant starts the survey, consistent with standard practice for online survey research. Ethical approval has been granted from the WVU Institutional Review Board (IRB) #2205571104.
Status and timeline
At the time of manuscript submission, the research will have just commenced recruitment of participants. Tentative survey rounds timeline is outlined in Table 2. All dates are subject to change and the hybrid introductory meeting is optional.
Discussion
This study protocol focuses on the conduct of a Delphi consensus-building process to determine what are the minimum items necessary in a reporting guideline for the clear and complete reporting of aromatherapy-focused research in humans. To ensure that the resulting reporting guideline reflects a high degree of agreement among the expert panelists, a global outreach for participation has been organized.
While use of the Delphi process is on the rise across various disciplines, there is no set method by which it can or should be conducted [10]. It is suggested that the epistemological, methodological, and empirical foundation be carefully considered and reported. As closely as possible, this Delphi protocol integrates these recommendations.
Epistemological underpinnings rest on aromatherapy as a professional practice with formal education, safety, and practice standards as opposed to “do-it-yourself” therapy requiring no formal training [16–18]. Therefore, a realist perspective is applied where we assert that the Delphi technique in the chosen sample should be able to produce a relatively unbiased approximation of “true” knowledge [28].
Methodological underpinnings support sample selection, survey instrument, a priori rounds, feedback, evaluation, results, transparency about quality of data interpretation, discussion and limitations, and plans for dissemination. There is evidence that reporting guidelines improve the reporting quality of empirical studies [29]. This study is specifically designed to support this outcome.
The efforts of ARQAT and publication of the TREATS lay the foundation for many of the items included in Round 1 of the Delphi survey [8, 30, 31]. In addition to the 38 items in TREATS, 10 additional items were added in response to feedback and research since TREATS was published. For example, section 1 was added to allow for feedback about items to include in the title. Also, sustainability is considered with two new items in section 3. Comments are invited during Rounds 1 and 2 to allow further items to be added during Round 1.
Strengths of this study include rigorous pilot testing, use of items from the TREATS, use of best practice in Delphi studies, and aiming for a high level of global involvement. First, rigorous pilot testing of the study was completed during 2024. This included the online survey platform, the supporting documents, and the study questions. Mock Rounds 1 through 3 were completed, the data analyzed, and changes made to help ensure clear results. This included the decision to add a scale question “Not my area of expertise” and to remove any response with this designation from the calculations [32]. This will enhance the quality of the responses, allowing those without expertise to decline answering items. Limitations include language and technology. Allowing only those who can read and write English and are able to participate in the online survey process to participate could limit responses.
Conclusion
The aim of this study is to create an aromatherapy research reporting guideline to support clear and complete reporting of this aspect of research. The guideline will provide an extension to existing reporting guidelines. This will contribute to the growing repository of resources for researchers of integrative modalities such as aromatherapy and serve as support for editors, peer-reviewers, and policy makers to identify high-quality aromatherapy research in humans that can be used in policy and practice.
Acknowledgments
The authors would like to acknowledge Amanda May-Fitzgerald, Denise Joswiak, and Bethany Unger for their significant contribution to this manuscript. We also acknowledge all past and present members of ARQAT (S4 File ARQAT Member List) including Michelle Cohen, Jerelyn Resnick, Donna Audia, Janet Tomaino, Barb Kurkas Lee, William McGilvray for their foundational contributions to this project. Additionally, thanks are extended to the WVU School of Nursing for their generous support and ongoing belief in nurse scientists as we explore the importance of comfort, caring, and the healing modality of aromatherapy in healthcare and nursing.
References
- 1. Cao X, Zhou J, Liu J, Chen H, Zheng W. Aromatherapy in anxiety, depression, and insomnia: A bibliometric study and visualization analysis. Heliyon. 2023;9: e18380. pmid:37519641
- 2. Koo M. A bibliometric analysis of two decades of aromatherapy research. BMC Res Notes. 2017;10: 46. pmid:28100267
- 3. Ball EL, Owen-Booth B, Gray A, Shenkin SD, Hewitt J, McCleery J. Aromatherapy for dementia. Cochrane Database of Systematic Reviews. 2020 [cited 6 Nov 2021]. pmid:32813272
- 4. Hines S, Steels E, Chang A, Gibbons K. Aromatherapy for treatment of postoperative nausea and vomiting. Cochrane Database of Systematic Reviews. 2018 [cited 6 Nov 2021]. pmid:29523018
- 5.
Airmid Institute–Protecting medicinal and aromatic plants for future generations. In: Airmid Institute [Internet]. 2024 [cited 20 Sep 2024]. https://airmidinstitute.org/
- 6. Leon M, Woo CC. Olfactory loss is a predisposing factor for depression, while olfactory enrichment is an effective treatment for depression. Front Neurosci. 2022;16: 1013363. pmid:36248633
- 7. Woo CC, Miranda B, Sathishkumar M, Dehkordi-Vakil F, Yassa MA, Leon M. Overnight olfactory enrichment using an odorant diffuser improves memory and modifies the uncinate fasciculus in older adults. Frontiers in Neuroscience. 2023;17. Available: https://www.frontiersin.org/articles/10.3389/fnins.2023.1200448 pmid:37554295
- 8. Reven ME, Bowles EJ, Audia DD, Cohen MM, Joswiak DJ, Kurkas Lee BA, et al. Quality Appraisal of Research Reporting for Aromatherapy and Essential Oil Studies in Humans: Proposed Checklist for “Transparent Reporting for Essential oil and Aroma Therapeutic Studies”. Journal of Integrative and Complementary Medicine. 2024;30: 469–477. pmid:38010213
- 9.
Equator Network. 2018. https://www.equator-network.org/toolkits/developing-a-reporting-guideline/
- 10. Spranger J, Homberg A, Sonnberger M, Niederberger M. Reporting guidelines for Delphi techniques in health sciences: A methodological review. Zeitschrift für Evidenz, Fortbildung und Qualität im Gesundheitswesen. 2022;172: 1–11. pmid:35718726
- 11. Beiderbeck D, Frevel N, Von Der Gracht HA, Schmidt SL, Schweitzer VM. Preparing, conducting, and analyzing Delphi surveys: Cross-disciplinary practices, new directions, and advancements. MethodsX. 2021;8: 101401. pmid:34430297
- 12. Moher D, Schulz KF, Simera I, Altman DG. Guidance for Developers of Health Research Reporting Guidelines. PLoS Med. 2010;7: e1000217. pmid:20169112
- 13. Boulkedid R, Abdoul H, Loustau M, Sibony O, Alberti C. Using and Reporting the Delphi Method for Selecting Healthcare Quality Indicators: A Systematic Review. PLOS ONE. 2011;6: e20476. pmid:21694759
- 14. Whiting P, Wolff R, Mallett S, Simera I, Savović J. A proposed framework for developing quality assessment tools. Syst Rev. 2017;6: 204. pmid:29041953
- 15.
ICAN | International Clinical Aromatherapy Network. 2024 [cited 20 Sep 2024]. https://www.clinicalaromatherapynetwork.com/?from=logout
- 16.
AIA | Alliance of International Aromatherapists—Home. 2024 [cited 20 Sep 2024]. https://www.alliance-aromatherapists.org/
- 17.
NAHA | National Association for Holistic Aromatherapy. 2024 [cited 20 Sep 2024]. https://naha.org/
- 18.
IFPA | International Federation of Professional Aromatherapists. [cited 20 Sep 2024]. https://ifparoma.org/
- 19.
IFA | International Federation of Aromatherapists. [cited 20 Sep 2024]. https://ifaroma.org/en_GB/home
- 20.
CAOA | Canadian Alliance of Aromatherapy—Home. [cited 20 Sep 2024]. https://caoa.ca/
- 21.
CFA | The Canadian Federation of Aromatherapists. In: The Canadian Federation of Aromatherapists [Internet]. [cited 20 Sep 2024]. https://www.cfacanada.com/
- 22.
Abraroma. In: ABRAROMA [Internet]. [cited 20 Sep 2024]. https://aromaterapia.org.br/
- 23.
ARTHES | ARTHES Schweiz. 11 Dec 2019 [cited 20 Sep 2024]. https://arthes.ch/
- 24. Nasa P, Jain R, Juneja D. Delphi methodology in healthcare research: How to decide its appropriateness. World J Methodol. 2021;11: 116–129. pmid:34322364
- 25. Moonaz S, Nault D, Cramer H, Ward L. CLARIFY 2021: Explanation and elaboration of the Delphi-based guidelines for the reporting of yoga research. BMJ Open. 2021;11: e045812. pmid:34353794
- 26. Harris PA, Taylor R, Thielke R, Payne J, Gonzales N, Conde JG. Research electronic data capture (REDCap)–A metadata-driven methodology and workflow process for providing translational research informatics support. J Biomed Inform. 2009;42: 377–381. pmid:18929686
- 27. Harris PA, Taylor R, Minor BL, Elliott V, Fernandez M, O’Neal L, et al. The REDCap consortium: Building an international community of software platform partners. J Biomed Inform. 2019;95: 103208. pmid:31078660
- 28.
Popper K. The Logic of Scientific Discovery. 0 ed. Routledge; 2005.
- 29. Sarkis-Onofre R, Poletto-Neto V, Cenci MS, Moher D, Pereira-Cenci T. CONSORT endorsement improves the quality of reports of randomized clinical trials in dentistry. Journal of Clinical Epidemiology. 2020;122: 20–26. pmid:32068103
- 30.
Reven ME, Bowles EJ, Peppers-Citizen M, May-Fitzgerald AC, Audia DD, Cohen MM, et al. A quest for quality reporting in aromatic research: 2022 white paper. Bethany WV: Aromatic Research Quality Appraisal Taskforce ARQAT; 2022 p. 54. https://www.arqat.org/the-white-paper
- 31. Unger B, Reven M, Resnick J. Developing ARQAT (aromatic research quality appraisal taskforce) and a new era of aromatic research reporting. The International Journal of Professional Holistic Aromatherapy. 2023;12: 48–52.
- 32. Soriano JB, Murthy S, Marshall JC, Relan P, Diaz JV, WHO Clinical Case Definition Working Group on Post-COVID-19 Condition. A clinical case definition of post-COVID-19 condition by a Delphi consensus. Lancet Infect Dis. 2022;22: e102–e107. pmid:34951953