PONE-D-22-20904High seroprevalence of immunoglobulin G (IgG) and IgM antibodies to SARS-CoV-2 in asymptomatic and symptomatic individuals amidst vaccination roll-out in western KenyaPLOS ONE

Dear Dr. Awandu,

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Reviewers' comments:

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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: Yes

Reviewer #2: No

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

Reviewer #1: Yes

Reviewer #2: Yes

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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

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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

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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: I think that this manuscript should be accepted with minor revision in introduction or part of the Demographics in the Results section. I suggest that authors add data on numbers of registered cases from the beginning of the pandemic in these two counties and also data on number of registered cases for the observed period in both counties. Possibly a figure could be drawn on incidence of registered cases and specific incidences by observed age groups as well. This is a minor effort and i belive it would fir well with the rest of the text and give it more clear overall picture

Reviewer #2: In this manuscript, Awandu et al. report the seroprevalence estimate in 98 individuals presenting to Kisumu and Siaya Counties referral hospitals in western Kenya between December 2021-March 2022. The authors measured SARS-CoV2 IgG and IgM antibodies in blood specimens and detected viral RNA in nasopharyngeal samples using commercial kits following manufacturer instructions. Of the 98 subjects, the authors report that 44 were vaccinated fully (n=31) or partially (n=13). They say high IgG seropositivity in both vaccinated (86.7%) and unvaccinated (70.3%) individuals and claim that PCR testing did not predict the seropositivity within the study period. The study has several weaknesses, some of which are listed below.

In the serology data sheet, the authors report a total of 32 PCR positives. This includes 12 (38.7%) PCR positives among 31 fully vaccinated, 8 (61.5%) PCR positives among 13 partially vaccinated, and 11 (20.3%) PCR positives among 54 unvaccinated individuals. Interestingly, 26 (83.8%) of the 31 PCR positives have been reported to have SARS-CoV-2 IgG antibodies. While breakthrough infections are possible, it is unclear why such a large proportion of PCR positives have SARS-CoV-2 IgG Abs. It is also unclear why PCR positives are higher among vaccinated than unvaccinated (47.7% (23 of 44) Vs. 20.3% (11 of 54).

The authors state that they have used commercial kits following manufacturer instructions. It is unclear if the authors have tested pre-pandemic samples to validate the commercial assay specificity.

Authors report the IgG and IgM results as ratios. However, the methods described in line 124 are unclear about how ratios were calculated from optical densities.

The number of vaccinated individuals reported in the abstract (n=30) and the serology data sheet (n=31) do not match.

Authors report that about 26 of 98 were asymptomatic. It will be helpful to clarify how asymptomatic were referred to the hospitals. Are these asymptomatic people exposed to people previously infected with SARS-CoV-2?

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Reviewer #1: No

Reviewer #2: No

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High seroprevalence of immunoglobulin G (IgG) and IgM antibodies to SARS-CoV-2 in asymptomatic and symptomatic individuals amidst vaccination roll-out in western Kenya

PONE-D-22-20904R1

Dear Dr. Awandu,

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,

Adriana Calderaro

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 #1: All comments have been addressed

Reviewer #2: 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 #1: Yes

Reviewer #2: Yes

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

Reviewer #1: Yes

Reviewer #2: Yes

**********

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 #1: Yes

Reviewer #2: 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 #1: Yes

Reviewer #2: 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 #1: I think all issues have been addressed and paper should be accepted. Paper is well written, all reviewers questions were met. Results are described clearly, Discussion is well referenced and limitations support the conclusion.

Reviewer #2: (No Response)

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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 #1: No

Reviewer #2: No

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