Infection Rate and Risk Factors of SARS-CoV-2 Infection in Retail Workers at the Onset of the COVID-19 Pandemic, Quebec, Canada

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The title of the manuscript reflects its content. The introduction orients the reader to the topic, discussing what is already known and what gaps exist in the literature. The authors clearly state the aim of the study. While the materials and methods section covers most aspects, other aspects of quantitative studies are not discussed. The results are well presented in both narrative and tabular form. The discussion compares the findings to previous literature and explains the meaning of the findings. The conclusion is based on the findings of the study.

MAJOR REVISIONS

Abstract

1. There should be background statements at the beginning of the abstract.

2. Statements on methods should be added to the abstract.

Materials and methods

3. Authors should explain how the sample size was determined.

4. What were the exclusion criteria for the participants?

5. What sampling method was used in the study?

Results

6. Add a table that shows the characteristics of participants.

7. Lines 156-160 should be moved to the introduction since they are not results.

8. Lines 162-167 should be added to the materials and methods.

References

9. Reference 21 should be appropriately formatted.

MINOR REVISIONS

10. In line 148, the authors state, ‘Infection was documented in 56 (32%) participants who did not reported symptoms.’  ‘Reported’ must be replaced with ‘report’

11. In lines 148-149, the authors state, ‘None of the participants had an infection severe enough to require hospitalization at baseline or per study.’ Replace ‘per’with ‘during the’

 

 

Comments on the Quality of English Language

Minor editing required

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The data consist of an 18-month follow-up from April 20th, 2021, to October 3rd, 2022 with up to five visits every 12±4 weeks. Each participant was in the study for a maximum of 48 weeks = 11 months. Total = 304 individuals.

 

With Figure 3 several questions arise, is the variable “education” really important in this study? Biases are observed in the classes and/or categories, since they are very unbalanced, for example, it is evident that between 60-75 years of age there is very little representation of patients, since people are undergoing retirement and are not active. The same happens with the variables related to smoking, influenza vaccine, work region, they are very unbalanced. Therefore, the crude Cox regression results are to be expected due to the bias of the data. 

 

Although the Cox regression methodology is well applied, it is important to assess the robustness of the results by adjusting for additional variables. Specifically, the vaccination variable should be considered in more detail, given that workers may have shown different trends in adherence to preventive measures. This could also help control for potential selection bias.

 

It is suggested that additional graphs illustrating the association between vaccination, type of work and other specific factors before and after relaxation of sanitary measures would facilitate understanding of the findings. For example, graphs comparing infection rates in workers of different ages and working hours could help to better communicate the relevance of these factors.

 

It would be interesting to see how age relates to comorbidities e.g., the older the age the more comorbidities?

 

It might be useful to specify variations in worker interactions in each type of occupation to justify the differential exposure assumption.

 

It would be beneficial to include a discussion that explores in depth how protective measures were implemented, especially in sectors such as restaurants where continuous use of masks is challenging.

 

The vaccination results suggest a reduction in the risk of infection with booster doses, indicating the efficacy of vaccination. However, it is important to recognize the limitations of the study in this regard, as the analysis cannot directly measure vaccine effectiveness due to possible self-selection and loss to follow-up. Further discussion of the biases inherent in this analysis would help to balance the conclusions.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

By and large, the study by Santerre et al. reveals no surprising new findings with regard to infections with SARS-CoV-2. Most of the observations in the manuscript could have been expected, as similar results have already been shown in numerous other studies.

Nevertheless, the study was conducted well and convincingly. The results have been presented clearly and accurately. I therefore see no reason not to publish this study, as it would expand existing knowledge on this topic.

However, the authors should clarify two points before publication:

1.       The authors describe that older people were less affected by infections than younger people. In the discussion, they provide several reasons for this, which are also plausible. As one reason, they themselves mention a possibly better vaccination of this group of people. Can the authors not prove this assumption with existing data? Have possibly more older people received a third vaccination than younger people? Can the authors establish a correlation based on their available data? 

2.       For me, the finding that the BMI had no influence on the incidence of infection is very surprising. The authors do not discuss this point at all in the manuscript. Why could this be the case? There are numerous studies that show that being overweight or obese is a risk factor for infection and that the infection is often more severe in this group of people. The authors should discuss this point and this discrepancy.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have adequately addressed all my comments.

Reviewer 2 Report

Comments and Suggestions for Authors

thank you for responding to each suggestion and specifying the limitations.