PONE-D-21-02405

SARS-CoV-2 transmission in students of public schools of Catalonia (Spain) after a month of reopening

PLOS ONE

Dear Dr. Llupià,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

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We look forward to receiving your revised manuscript.

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Beatriz da Costa Thomé, MD, MPH, PhD

Academic Editor

PLOS ONE

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Additional Editor Comments:

Valuable article that discusses a relevant aspect of Covid transmission that relates to the contribution of school. A major strength is making use of publicly available aggregated data. The data however has important limitations that should also limit the strength of the conclusions. Furthermore, the discussion misses in my opinion other references in which school transmission of course reflected community transmission (one of the findings of this article), but didn't contribute so importantly to overall transmission. These should be added to the discussion.

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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: Yes

Reviewer #2: Yes

Reviewer #3: Partly

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

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: 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

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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

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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: The manuscript by Anna Llupià et al. investigates the impact of re-opening schools in the transmission of SARS-CoV-2 through a retrospective cohort using available public data. The manuscript's strengths are the population level of the data. They found an association between the number of cases in the first two weeks of re-opening with the increased incidence of cases 2-3 weeks later, particularly in secondary schools. Although these findings are significant and obtained via adequate statistical analysis, some conclusions and inferences need to be more suitable when presenting and discussing the results. The existence and the impact of within school transmission can not be inferred with the data available and with this study design. When adjusted by community incidence (BHA), the RR is significant but very mild (RR 1.002). Also, the increase in incidence at week 4-5 was higher when the schools had zero cases in the first two weeks compared to those with at least one case (Figure 1). It does not reject the study and its findings, but the impact of within school transmission should be cautiously stated and discussed better.

Minor comments:

- When discussing the higher incidence in secondary schools, the authors mentioned several behaviours and social reasons, but they do not mention the higher number of students per class (20 vs 30 students, as mentioned in the introduction).

- The methods section in the abstract is a bit confusing. I suggest rewriting.

- Page 2 / Line 9 – wrong capital letter in To; two "s" in sSARS-CoV-2

- Page 10 / Line 18 - "may have contributed"

- Page 10 / Line 21 – no comma after Sapin

- Page 11 / Line 19 – ineffective

- Page 11 / Lines 25-26 – confusing sentence; suggest rewriting

- Page 12 / Line 2 – SARS-COV-2

- Page 13 – paragraph starting in line 5 is too long and hard to read.

Reviewer #2: Please review line 9 page 4

The article is relevant to this moment of school reopening demand, data presents the impact of reopening to the number of cases and the risk of it. If possible, it would be interesting to consider impact of vaccination in these process.

Reviewer #3: Relevant study, describes appropriately the SARS-CoV-2 transmission in public school students in the first five

4 weeks of the 2020-21 academic year in the public schools of Catalonia-Spain, using available aggregated data.

Simple analysis and it is not described in sufficient detail. The study presents the results of original research, but the analysis must be describe in sufficient detail. Also, the conclusions are not presented in an appropriate fashion.

The authors must highlight the limitation of this study related to data were aggregated at the school level and it was not possible to know if different SARS-CoV2 infection cases shared the same place or extracurricular activities or which was their age group.

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Reviewer #1: No

Reviewer #2: Yes: Mariana Cabral Schveitzer

Reviewer #3: No

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SARS-CoV-2 transmission in students of public schools of Catalonia (Spain) after a month of reopening

PONE-D-21-02405R1

Dear Dr. Llupià,

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,

Beatriz Thomé, MD, MPH, PhD

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Thanks for responding to the comments made during the first review of the manuscript. A few remaining (minor) suggestions are shared for the authors consideration as they proceed with the final version of the article.

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

Reviewer #3: 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

Reviewer #3: Yes

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

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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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 #1: Yes

Reviewer #2: Yes

Reviewer #3: 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

Reviewer #3: 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: After the first review, the authors provided accurate responses, making the manuscript neater and more precise after the revision. I do not suggest any significant corrections.

Minor comments:

Line 83, 243, 244 – I suggest adding the year (2020) to make it easier for future readers.

Title and first line in Table 2 and Line 281 – Correct SARS-CoV2 to SARS-CoV-2.

Line 221 – Delete “describe”.

Line 253 – I would clarify "COVID-19 outcomes" (worst outcome if children in the household?).

Line 319 – correct “all,after”.

Reviewer #2: The update was very helpful. There are considerations today regarding the PCR negative results as the only criteria to return to activities. A possible approach would be to consider clinical observation and patient lack of symptoms. How is this discussion in Catalonia?

Reviewer #3: (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: Yes: Vinicius Adriano Vieira

Reviewer #2: No

Reviewer #3: No