Comparison of the Basic Reproduction Numbers for COVID-19 through Four Waves of the Pandemic in Vietnam

Round 1

Reviewer 1 Report

The authors have done a unique study here, which is timely, interesting. I think the manuscript is “brief” (no issue), but has some “shortcomings” with regards to “narrative and discussion”. After reading the whole manuscript, I feel like reading another paper that used the concept of the current paper (particularly after reading the Intro and Conclusion). There could be some changes needed to the narrative's flow and contents. Why did the researchers undertake a study specifically for Vietnam? why is Vietnam unique? It could be more crucial to (i) introduce, (ii) discuss on the impacts of the COVID-19 wave series. Also, the findings are there, but have not been discussed to full extent. Please concentrate more on the findings that are directly related to your hypothesis. I have provided several remarks that needs to be addressed by the authors. Please revise your manuscript in accordance with the comments and your personal assessments. Thank you.

 

INTRODUCTION

Please provide a reference for the following:

“R0 can be defined as an average number of secondary infections …”

 

I thought that Vietnam has done good enough in terms of vaccination? In fact, in year 2022, the following may be a bold statement, and needs to be adjusted and supported.

“Providing vaccination for the whole population is hard to achieve. Therefore, vaccinating a specific proportion of the population could work as a protective wall for other susceptible persons against getting the infection. This proportion can be calculated depending on the R0 of the disease”

 

 

The following statement is important, please quote accordingly.

“The R0 value depends not only on the biological characteristics of the disease but also on the social habits of the population”

 

When the authors state “up to now”… please include the date.

 

What are the issues concerning different methods to determining R0? please discuss more.

 

Again, please create a narrative that connects between R0 and the following statement:

“it is still unclear how many people will need to be vaccinated to achieve herd immunity”

 

 

FIGURES

Suggest some cosmetic changes to figures – easy edits.

What are the values of “Ic” within the figures? …if %, one decimal is probably sufficient.

 

DISCUSSION

 

It seems difficult to associate the following statement with the previous sentences (study findings); please update accordingly.

“As a result, the vaccination coverage needed to achieve herd immunity against COVID-19 will be more in high-density population provinces with higher R0 values”

 

Here is very important, and perhaps several sentences or one paragraph is needed here. Please try to compare and contrast your findings (using the EG and ML methods) with other studies that used the same methods, and different methods.

 

The following is not clear, please rephrase:

“The highest R0 value in HCM city could be not reflected exactly in real dynamics due to being affected by the late discovery of new clusters of infections.”

 

In your limitations, you made the same statement twice: “confirmed cases data”

 

When I read the conclusion, there is no conclusion directly about your findings. Those are almost appeared as general support to your findings.

 

I think the ethical statement is not fully accurate, perhaps you can tell that you have used publicly available data, or sourced from somewhere?

“No ethical approval was required as no human or animal subjects were used in this study”

Author Response

We thank the reviewer very much for your comments. 

Author Response File: Author Response.pdf

Reviewer 2 Report

This work is original, novel and important to the field.

The structure is good and the language is appropriate.

The paper will be ready for publication after major revision.

The paper should be revised based on the attached file.

 

Comments for author File: Comments.pdf

Author Response

We thank the reviewer very much for your comments and suggestions! We have revised the manuscript as you suggested.

Author Response File: Author Response.pdf

Reviewer 3 Report

Summary: Authors estimated the R0 values of the COVID-19 through four waves of pandemic in Vietnam using the EG and ML methods to calculate the minimal vaccination coverage in different populations.

Major comments:

1. Authors need to explain why the used the EG and ML methods and what are the potential alternatives to these methods for calculating R0.

2. The paper did not discuss the relationship between different variants, such as Delta or Omicron, with different R0 values.

3. According to WHO, herd immunity is the protection from an infectious disease that happens when a population is immune either through vaccination or immunity developed through previous infection, while authors ignored the impact of previous infection in their discussion regarding herd immunity and how it can be impacted by R0.

Author Response

We thank the reviewer very much for your comments and suggestions! We have revised the manuscript as you suggested.

Response to Reviewer 3 Comments

 

Point 1:

Authors need to explain why the used the EG and ML methods and what are the potential alternatives to these methods for calculating R0.

 

Response 1:

Thank you very much for bringing up this concern. We have added some information about the EG and ML methods as well as other methods as follows:

“In addition to EG and ML methods, other methods such as the sequential Bayesian method, the SIR model… also used for the estimation of R0 of COVID-19 [12-16]. In these studies, the R0 value from the EG method was lower than from other methods and the R0 value from the ML method was highest in all methods. Additionally, the ML method has been used most in the estimation of R0 of COVID-19 [12, 13, 15].”

 

Point 2:

The paper did not discuss the relationship between different variants, such as Delta or Omicron, with different R0 values.

 

Response 2:

Thank you so much for your constructive comment. We have added the following information in the discussion.

“The new occurrence of the Delta Variant has been indicated to be more severe than the Alpha variant with a higher R0 value in the previous study [35].”

 

Point 3:

According to WHO, herd immunity is the protection from an infectious disease that happens when a population is immune either through vaccination or immunity developed through previous infection, while authors ignored the impact of previous infection in their discussion regarding herd immunity and how it can be impacted by R0.

 

Response 3:

Thank you very much for bringing up this concern. We have added the information as follows:

“Herd immunity threshold is minimal immune either through vaccination or immunity developed through the previous infection which depends on the value of R0. However, vaccination helps to improve protection among persons who had a previous infection. In addition, hybrid immunity resulting from previous infection and booster vaccination granted the strongest protection."

Reviewer 4 Report

The manuscript under review provides an analysis of the basic reproduction numbers for COVID-19 during 4 waves of the pandemic in Vietnam. The Authors collected the data about the number of confirmed COVID-19 cases from 21^st January 2020 to 16^th November 2021. I think it is a pretty good manuscript, even if the topic is of average interest. I have a few  comments:

-          - In the abstract, this sentence should be re-written: “The fourth wave-the most severe, especially in southern provinces were more affected, the highest R0 was observed in Ho Chi Minh city”.

-          - In materials and methods, the study design should be explicated.

-          - Page 6, figure 2’s caption: I think the Authors should add “2020” after January (“from 21^st January 2020 to 16^th November 2021”)

-         - Page 6, figure 2, is the figure complete? If yes, there is no need to specify “from A to D” in the caption, because there are only figures from A to D.

-          - The conclusions are too short, please implement them, for example adding a very short summary of the results.

-           - A whole manuscript English revision is required

-          - I suggest implementing the reference list with the following: 10.5005/jp-journals-10071-23649; 10.3390/vaccines10020308; 10.1080/21645515.2020.1865046

Author Response

We thank the reviewer very much for your comments and suggestions! We have revised the manuscript as you suggested.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The manuscript has been revised according to the feedback/comments of the reviewers.

Reviewer 2 Report

The paper is well-revised.

It is ready for publication.

Reviewer 4 Report

The Authors adressed all the issues I highlighted. I think the manuscript improved and now it is ready to be published.