PONE-D-23-03744Covid-19 hospitalisations and all-cause mortality by risk group in FinlandPLOS ONE

Dear Dr. Cansel,

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Academic Editor

PLOS ONE

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Additional Editor Comments:

Dear Authors

Reviewers suggested to revise your manuscript, if you wish to proceed, we may proceed to the final acceptance to your paper.

If you agree, please proceed the revision addressing the reviewer's comments

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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

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

Reviewer #1: Yes

Reviewer #2: Yes

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Reviewer #1: Yes

Reviewer #2: Yes

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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: First, I appreciate the authors efforts in conducting and presenting this interesting study. I understand that the peer review process can be challenging, but please rest assured that my aim is to provide constructive feedback that will help to improve the quality of your manuscript and contribute to its overall success.

1. Please use the term "COVID-19" instead of "Covid-19".

2. Abstract: The abstract presents a clear and concise overview of a retrospective observational study on COVID-19 in Finland, including the study's objectives, methods, and key findings. The abstract is written in a scientific style, and the language used is appropriate for a scientific audience. Overall, the abstract appears to be well-written and informative.

3. Introduction: Some minor improvements can be suggested as follows-

a) In the line 42, it should be noted that the World Health Organisation (WHO) announced COVID-19 as a global pandemic, not just "announced" it.

b) In the lines 44 and 45, it should be noted that while most people infected with COVID-19 have mild-to-moderate symptoms, a significant proportion may still experience severe symptoms leading to hospitalization and death.

c) In the line 46, it should be noted that while certain risk groups are more likely to develop severe COVID-19, the disease can affect anyone regardless of age or pre-existing conditions.

d) In the line 47, please add Chronic respiratory diseases as pre-existing condition, you may also add diabetes, because people with diabetes s and COVID-19 often need invasive ventilation care and need intensive care unit (ICU) due to their likelihood of developing Acute Respiratory Distress Syndrome (ARDS) -Aging (Albany NY). 2020 Apr 15; 12(7): 6049–6057. Published online 2020 Apr 8. doi: 10.18632/aging.103000)

e) In the line 53 and 54, it should be noted that while COVID-19 vaccines can reduce the burden of the disease, they do not completely eliminate the risk of severe symptoms or transmission.

f) In the line 56 and 57, it should be noted that while early treatment may prevent severe COVID-19, it is not always effective and should be used in combination with preventive measures and vaccination.

(Overall, the introduction provides a reasonable and accurate overview of the current understanding of COVID-19 and its risk factors, while acknowledging some uncertainties and the importance of ongoing research.)

4. Methods: There are no major scientific writing errors in the methods. However, here are a few minor suggestions for improvement-

a) In the line 72, the phrase "summary level statistics" could be clarified for readers who may not be familiar with the term. For example, "This study used aggregate data obtained from the Finnish Institute for Health and Welfare's registers..."

b) In the lines 83, 84 and 85, "The results are analysed based on patients identified from Hilmo..." could be rephrased for clarity, for example: "Data from Hilmo was used to identify patients for analysis, and any differences between TTR and Hilmo patients are reported in supplementary materials (S1 and S2 Tables)."

c) In the lines 113 and 114, it may be helpful to specify which types of visualizations were used for the descriptive data analysis.

d) In the line 119, it may be helpful to provide a brief explanation of the infection hospitalization rate (IHR) and the case fatality rate (CFR), for readers who may not be familiar with these terms.

e) In the lines 122 and 123, the phrase "divided by the total number of individuals with a COVID-19 infection" could be clarified by specifying whether this refers to the total number of infected individuals in the entire population or only within each risk group.

5. Results: Well written and described

6. Discussion:

a) In the lines 201 to 205, elderly with COVID-19 infection was only indentified as a risk group in this study? If not, please add some other risk factors points like Chronic lung diseases, diabetes, cardiovascular diseases. My suggestion stands: https://doi.org/10.1371/journal.pone.0233147; https://doi.org/10.1016/S2213-2600(20)30116-8.

Reviewer #2: REVIEWERS COMMENTS- PONE-D-23-03744

The study PONE-D-23-03744: Covid-19 hospitalizations and all-cause mortality by risk group” in Finland” aimed to identify which risk groups are at the highest risk of having

severe Covid-19 infection, sever disease leading to hospitalization or death in Finland. The authors used retrospective observational study with Finnish registry data to answer this question.

On the whole, the manuscript is well written, clearly followed and easily understood.

Below are a few issues for authors consideration;

Background

Line 61: why Omicron in particular?

Materials and methods

Line 76-77: was the 2020 data unavailable especially the later months of the year

Discussions

Line 197-199: please cross-check this claim to be sure- there seems to many studies in that region reporting covid-19 severities and related mortalities vs risk factors

Line 201- 205:

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Reviewer #1: No

Reviewer #2: No

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COVID-19 hospitalisations and all-cause mortality by risk group in Finland

PONE-D-23-03744R1

Dear Dr. Cansel,

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.

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Kind regards,

K M Amran Hossain, MScPT

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Thank you for the revision of the manuscript

Reviewers' comments: