PONE-D-22-32927SARS-CoV-2 infection- induced seroprevalence among children and associated risk factors during pre- and omicron-dominant wave, from January 2021 through November 2022, Thailand: Longitudinal studyPLOS ONE

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“This research was financially supported by the Health Systems Research Institute (HSRI), National Research Council of Thailand (NRCT), the Center of Excellence in Clinical Virology, Chulalongkorn University, and King Chulalongkorn Memorial Hospital, MK Restaurant Group Aunt Thongkam Foundation, BJC Big C Foundation, and the Second Century Fund (C2F), Chulalongkorn University”

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“This work was supported by the National Research Council of Thailand, the Health Systems Research Institute, the Center of Excellence in Clinical Virology of Chulalongkorn University, King Chulalongkorn Memorial Hospital, and the Berli Jucker Company Big C foundation. Nungruthai Suntronwong reports that financial support was also provided by the Second Century Fund Fellowship of Chulalongkorn University. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.”

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Partly

Reviewer #3: Partly

Reviewer #4: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: No

Reviewer #4: No

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3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: No

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

Reviewer #4: No

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: This study by Suntronwong et al describes “SARS-CoV-2 infection- induced seroprevalence among children and associated risk factors during pre- and omicron-dominant wave, from January 2021 through November 2022, Thailand: Longitudinal study”. It will be nice study if the authors will consider few points and answer it properly:

Abstract

1. At end of abstract, authors should emphasis on novelty and impact of the study.

Introduction:

I. What was the criterion for selection of pediatric population?

I. Is any similar type of data was reported from any part of the world. If yes, then please include in introduction?

II. Authors are also suggested to cite the some of the recently published papers regarding the longitudinal study regarding SARS-CoV-2 infection- induced seroprevalence.

Result and discussion

• Why the samples were taken from Center of Excellence in Clinical Virology, Chulalongkorn Memorial Hospital, Bangkok, Thailand.

• What was the control for this study?

• Why these particular samples were taken?

• What is the importance of this study as the samples were taken from specific area?

• Why the samples were taken in between January and December?

• As the time duration is too long where there is possibility of change in sero-positivity.

Conclusion

Please add impact of study on the national level.

Reviewer #2: 1. Abstract. Briefly present the inclusion/exclusion criteria in the ‘method’ part. Children age range should be disclose too.

2. In introduction. Authors are encouraged to provide the Omicron prevalence among children.

3. In introduction. Please include the necessity of performing this study especially in the midst of global emergence of Omicron VOC (https://www.sciencedirect.com/science/article/pii/S1876034122003161?via%3Dihub#fig0010)

4. Please explain the impact of low seroconversion among CoronaVac recipients to the results of your study. (Ref: https://www.narraj.org/main/article/view/71)

5. High population burden of Omicron variant (B.1.1.529) has been associated with the emergence of severe hepatitis of unknown etiology in children (ref: https://doi.org/10.1016/j.ijid.2022.05.028) How this finding is relevant to your study?

6. There is a good report titled “The race for clinical trials on Omicron-based COVID-19 vaccine candidates: Updates from global databases” (https://www.narraj.org/main/article/view/88) which authors may wish to incorporate in their discussion.

7. It is interesting that there is no meaningful difference on the infection-induced seroprevalence between boy and girl. Meanwhile, gender has been an associated factor for vaccine efficacy (favouring men; ref: https://www.mdpi.com/2076-393X/9/8/825). Please discuss.

8. Pay attention on the grammatical errors.

Reviewer #3: The authors provide an article on the important topic of SARS-CoV-2 seroprevalence in children during the COVID-19 pandemic in Thailand. The authors estimated infection-induced seroprevalence considering pre- and Omicron waves and reported factors associated with seropositivity.

Although the manuscript addresses a relevant topic and has some strengths, there are major statistical and presentational issues, outlined below.

1. To estimate the seroprevalence of SARS-CoV-2 the authors relied on a longitudinal study of pertussis vaccine immunity. The serum samples were collected from the participants between January 1, 2021, through November 9, 2022, in small amounts each month. Seroprevalence of SARS-CoV-2 was estimated for the overall study period, pre-omicron period, omicron period, and on a quarter and monthly basis. The method description is incomplete and inconsistent with the results section. Quarter/Monthly estimates are shown in figure 2 and figure 3 but are not mentioned in the methods section. A number of samples collected monthly and 95% confidence intervals for monthly/quarterly estimates also are not reported.

2. Figure 2 is too busy and difficult to follow. It has two Y axis, on the right side of the graph the authors present the number of positive samples, and the scale range is from 0 to 800, it is not clear if the bars represent a number of positive samples or infection-induced seroprevalence. Also, only 438 samples were collected during the study, why axis limit is established at 800?

3. As it follows from the description of the method, most of the participants were followed up and observed twice, but some of them were new recruitments during the omicron wave. This inclusion strategy resulted in two partially overlapping groups, one observed in pre-Omicron and another in the Omicron predominance period). The authors performed several comparisons of proportions, and sometimes comparisons presented in Table 1 are made between overlapping groups. The authors used the chi-square test for all comparisons, however, the use of the classical chi-square test does not seem appropriate when the groups are overlapping.

4. The authors also aimed to identify Factors associated with infection-induced seropositivity and reported risk ratios. The risk ratio is a measure of association used in cohort studies. In a cohort design, all the participants should be free of the outcome at baseline. According to the information presented by the authors, it is not the case, some of the participants were seropositive at recruitment, so the risk ratio does not seem to be an appropriate measure of association in this particular case.

Reviewer #4: The researchers conducted a longitudinal study to examine SARS-CoV-2 infection-induced seroprevalence in children and to estimate the risk variables for seropositivity. Anti-nucleocapsid (N) IgG and anti-receptor binding domain (RBD) IgG were identified using a chemiluminescent microparticle immunoassay (CMIA), and anti-RBD Immunoglobulin (Ig) was detected using an electrochemiluminescence immunoassay (ECLIA). The study addresses an important issue and has performed good comparison of effect of vaccination vs natural infection.

This reviewer has some concerns and suggestions for the authors to consider:

Specific comments:

1. Line 79: In the introduction section, it is important to mention in the manuscript regarding which vaccines are inactivated vaccines, which ones are mRNA vaccine etc to enable the understanding and relevance of this sentence and the overall rationale of this study. Same applies to the BNT162b2 vaccine described in this study.

2. Lines 85-91: These sentences need to be rephrased to enable understanding of their implied meaning. In addition, the Comment 1 is also relevant to make the rationale of the study.

3. Lines 188-191: This section needs to be re-phrased properly.

4. Was there any correlation of anti-RBD antibody levels with disease severity? Please mention it in the Results and Discussion section.

5. Why is just IgG employed for anti-receptor binding domain? Please explain the choice with supporting reference. Please also mention the limitations/disadvantages of using IgM based detection?

6. Please mention in the manuscript (with supporting references) if the anti-RBD IgG has neutralising potency.

7. Generalised comment: The language of manuscript needs major improvement. There are several grammatical mistakes. Please have it fixed.

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Reviewer #1: Yes: Dr. Gaurav Raj Dwivedi

Reviewer #2: Yes: Muhammad Iqhrammullah

Reviewer #3: No

Reviewer #4: No

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SARS-CoV-2 infection- induced seroprevalence among children and associated risk factors during the pre- and omicron-dominant wave, from January 2021 through December 2022, Thailand: A longitudinal study

PONE-D-22-32927R1

Dear Dr. Poovorawan,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

Harapan Harapan, MD, PhD

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #2: All comments have been addressed

Reviewer #4: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #2: Yes

Reviewer #4: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: Yes

Reviewer #4: I Don't Know

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4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #2: Yes

Reviewer #4: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #2: Yes

Reviewer #4: Yes

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #2: In general, authors have address all my previous concern, thereby can be accepted for publication. Nevertheless, I suggest author to include the justification of the time span for sera collection "from January 1, 2021

to December 14, 2022 ". Reasons for date selection should be disclosed in the method. Moreover, authors did not recruit control group, and this can be added as limitation of the study.

Reviewer #4: The revised version of the manuscript entitled "SARS-CoV-2 infection- induced seroprevalence among children and associated risk factors during the pre- and omicron-dominant wave, from January 2021 through December 2022, Thailand: A longitudinal study" can be accepted.

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7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #2: No

Reviewer #4: No

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