Willingness of Older Adults with Chronic Diseases to Receive a Booster Dose of Inactivated Coronavirus Disease 2019 Vaccine: A Cross-Sectional Study in Taizhou, China

Round 1

Reviewer 1 Report

The manuscript is generally  good developed and written. There are substantial revisions that I would like the authors to address and/or to consider.

Abstract:

1.      The abstract needs to be substantially revised and elaborated. Please provide year of study, instruments, sampling method, and used statistical software concisely and clearly.

2.      Please clarify “aged >60 years”:  only over the 60 or 60 years and above

Main Manuscript :

3.      First paragraph of introduction: please provide exact date of information

4.      Study design and data collection: sampling method? How sample were selected/ please clarify “valid data” / date of the study / how accuracy of data collection was assessed

5.      Literature search strategy: this section may be not relevant.  

6.      Table 4. is not necessary. It can be texted and incorporated in the introduction and discussion section

7.      Please provide research implications of the study

 

Author Response

Reviewer1:

The manuscript is generally good developed and written. There are substantial revisions that I would like the authors to address and/or to consider.

Abstract:

1.The abstract needs to be substantially revised and elaborated. Please provide year of study, instruments, sampling method, and used statistical software concisely and clearly.

Response: Thanks for the reviewer’s useful comments. We have revised in Abstract. Please see lines 16-26.

2. Please clarify “aged >60 years”:  only over the 60 or 60 years and above.

Response: Thanks for the reviewer’s useful comments. The age of the target population was 60 years and above.

We have revised in Abstract. Please see line 21.

Main Manuscript :

3.First paragraph of introduction: please provide exact date of information

Response: Thanks for the reviewer’s useful comments.

Since the COVID-19 global pandemic, more than 600 million people have been diagnosed and more than 6 million have died worldwide, as of September 16, 2022.

We have revised in Introduction. Please see lines 37-38.

4. Study design and data collection: sampling method? How sample were selected/ please clarify “valid data” / date of the study / how accuracy of data collection was assessed.

Response: Thanks for the reviewer’s useful comments.

We conducted a questionnaire survey in the geriatric outpatient department of Tai-zhou Hospital during between July 6 and August 11 in 2021. A total of 308 patients re-ceived the invitation.The participants completed a self-administered questionnaire by scanning a Quick Response code on their mobile smartphones, and they did so entirely voluntarily. Sample size determination using the G*Power software(ver. 3.1.9.7; Hein-rich-Heine-Universität Düsseldorf, Düsseldorf, Germany)[16,17].We used 2-sided testing, Odds ratio=2, Pr(Y=1| X=1) H0=0.5, α err prob=0.05, power (1-β err prob)=0.85,R2 other X=0.6.The minimum sample size was computed as 229.The inclu-sion criteria for this study were patients aged 60 years and above with non-oncological chronic diseases. Respondents who did not answer completely, contained unreasonable information were excluded..A total of 254 patients with valid data were enrolled in this study, with a response rate of 82.5% (254/308).

We have revised in Study design and data collection. Please see lines105-116.

5. Literature search strategy: this section may be not relevant.

Response: Thanks for the reviewer’s comment.

This section is an elaboration of the search method for Table 4, which we consider to be indispensable in the Method. Therefore Literature search strategy was retained

6. Table 4. is not necessary. It can be texted and incorporated in the introduction and discussion section.

Response: Thanks for the reviewer’s useful comments. We have expanded the content of Table 4.

7. Please provide research implications of the study.

Response: Thanks for the reviewer’s useful comments.

There are also different findings in this survey. First, The results of this study showed that 95.5% of those who completed the initial dose of the COVID-19 vaccine were willing to receive the booster dose. Therefore, the vaccination strategy for the booster dose should be focused on increasing the acceptance of the initial dose of the vaccine and encouraging individuals who have not yet received the initial dose to get vaccinated as soon as possible, thereby increasing the booster dose administration and maintaining the continuity of herd immunity. Second, the impact of older age and clinical stability of disease control on the willingness of older adults with chronic conditions to receive COVID-19 vaccine boosters is not negligible.

We have revised the Discussion. Please see lines 291-299.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

First of all I would like to thank for the opportunity to review this paper. The outbreak and spread of the pandemics have been an issue of critical concern globally, posing a significant threat to the health sector globally. Actually, the vaccination campaign is the first method to counteract the COVID-19 pandemic; however, sufficient vaccination coverage is conditioned by the people’s acceptance of these vaccines, especially in at-high-risk group of population, such as elderly. In this context, aim of the paper under review is to to investigate the willingness to receive a COVID-19 vaccine booster and its influencing factors a sample of patients from a tertiary Hospital in China.

The subject under study is certainly important, especially in the historical period we are experiencing. The article presents interesting results but, but it is nevertheless believed that it must be improved before publication due to its very local impact, the small sample and some methodological concerns. I would like to encourage authors to consider several issues to be improved.

Title: it can be improved, highlight the object and the kind of study.

Introduction: The authors should make clearer what is the gap in the literature that is filled with this study. The authors must better frame their study within the vast body of literature that addressed the issue of knowledge regarding the disease and its relation to acceptance of COVID-19 vaccination in elderly (refer to articles with DOI: https://doi.org/10.3390/ijerph182010872) also at international level. Moreover, the study aims must be better clarified at the end of the introduction section.

Methods: The survey was conducted using a non-standard questions. The use of an unreliable instrument is a serious and irreversible limitation. A validation process must be performed to evaluate the added questions to a standard questionnaires. What about reliability, intelligibility and validation index? Was a pilot study performed?

The enrolment procedure must be specified. How did the authors choose the way to select the sample? This can represent a great bias origin. How did they avoid the selection bias? The authors do not propose a minimum sample size, what is the reference population? How large is it? It must be stated in the methods section Without the numerical identification of the reference population is not clear the validity of the study. A non-representative sample is by its self a non-sense-survey.

Statistical analysis: I suggest to insert a measure of the magnitude of the effect for the comparisons. Please consider to include effect sizes.

Discussion: I also suggest expanding. Emphasize the contribution of the study to the literature. The discussion must be updated with the discussion regarding the relation between knowledge and acceptance in different counties, a paragraph should be added with a proper reference (see the above mentioned reference). The Authors should add more practical recommendations for the reader, based on their findings. Also, the section of limitations and future search is also very short, the Authors could elaborate on that.

Author Response

Reviewer2:

First of all I would like to thank for the opportunity to review this paper. The outbreak and spread of the pandemics have been an issue of critical concern globally, posing a significant threat to the health sector globally. Actually, the vaccination campaign is the first method to counteract the COVID-19 pandemic; however, sufficient vaccination coverage is conditioned by the people’s acceptance of these vaccines, especially in at-high-risk group of population, such as elderly. In this context, aim of the paper under review is to to investigate the willingness to receive a COVID-19 vaccine booster and its influencing factors a sample of patients from a tertiary Hospital in China.

The subject under study is certainly important, especially in the historical period we are experiencing. The article presents interesting results but, but it is nevertheless believed that it must be improved before publication due to its very local impact, the small sample and some methodological concerns. I would like to encourage authors to consider several issues to be improved. 

1.Title:it can be improved, highlight the object and the kind of study.

Response: Thanks for the reviewer’s useful comments.

We have revised the title to “Willingness of older adults with chronic diseases to receive a booster dose of inactivated coronavirus disease 2019 vaccine: a cross-sectional study in Taizhou, China”

Please see lines 2-4.

 

Introduction:

2.The authors should make clearer what is the gap in the literature that is filled with this study.

Response: Thanks for the reviewer’s useful comments.

There are few studies on willingness to receive COVOD-19 vaccine booster that focus on the population of older adults with chronic diseases, mostly the general adult population and healthcare workers. Questionnaires have also been widely used as a research method in previous studies on the intention to vaccinate the elderly with the initial doses of the COVID-19 vaccine. The existing study has shown that bad health conditions can reduce the willingness of older adults to receive the initial dose of COVID-19 vaccine.

We have revised in Introduction. Please see lines 88-94.

 

3.The authors must better frame their study within the vast body of literature that addressed the issue of knowledge regarding the disease and its relation to acceptance of COVID-19 vaccination in elderly (refer to articles with DOI: https://doi.org/10.3390/ijerph182010872) also at international level.

Response: Thanks for the reviewer’s useful comments.

In an Italian study, the elderly showed well knowledge about COVID-19 and its preventive aspects. The perceptions of the COVID-19 vaccine, particularly safety and efficacy, were positively associated with factors in the willingness to receive the initial dose in the general elderly population in various countries. Our study found that willingness to receive a booster dose in the elderly chronic disease patient population was similarly influenced by perceptions of COVID-19 vaccine safety and efficacy.

We have revised in Discussion. Please see lines 285-290.

4.Moreover, the study aims must be better clarified at the end of the introduction section.

Response: Thanks for the reviewer’s useful comments.

This study aimed to investigate the willingness of China's elderly chronic disease population to receive a booster dose of COVID-19 vaccine and further analyze the factors related to their willingness.Then provide a basis for promoting COVID-19 booster vaccination in the future to improve the extent of immune protection offered by the COVID-19 vaccine.

We have revised in Introduction. Please see lines 95-99.

 

Methods:

3.The survey was conducted using a non-standard questions. The use of an unreliable instrument is a serious and irreversible limitation. A validation process must be performed to evaluate the added questions to a standard questionnaires. What about reliability, intelligibility and validation index?

Response: Thanks for the reviewer’s useful comments. The survey was conducted using a non-standard questions. Since our questionnaire uses a non-scale format, it is difficult to test the reliability, intelligibility and validation indexes.

We have revised in Discussion. Please see lines 346-348.

 

4.Was a pilot study performed? 

Response: Thanks for the reviewer’s useful comments.

Referring to questionnaires from previously published articles by our team, the initial questionnaire for this study was formed by the expert meeting. There was a pilot study performed. In order to ensure the quality of the official questionnaire, 20 elderly patients with chronic diseases were invited to participate in an initial test at the hospital outpatient department, and then questions that were deemed unreliable were revised based on feedback from the test population. We finalized the final version of the questionnaire for this study through expert meetings again.

We have revised in Structured questionnaires and measurement. Please see lines 141-147.

 

5.The enrolment procedure must be specified. How did the authors choose the way to select the sample?

Response: Thanks for the reviewer’s useful comments.

We conducted a questionnaire survey in the geriatric outpatient department of Taizhou Hospital during between July 6 and August 11 in 2021. A total of 308 patients received the invitation. The participants completed a self-administered questionnaire by scanning a Quick Response code on their mobile smartphones, and they did so entirely voluntarily. The inclusion criteria for this study were patients aged 60 years and above with non-oncological chronic diseases. Respondents who did not answer completely, contained unreasonable information were excluded. The time taken to complete the questionnaire was converted logarithmically, and if it exceeded mean ± 3SD, it was considered an outlier and was also excluded from the analysis. A total of 254 patients with valid data were enrolled in this study, with a response rate of 82.5% (254/308).

We have revised in Study design and data collection. Please see lines 105-116.

 

6.This can represent a great bias origin. How did they avoid the selection bias?

Response: Thanks for the reviewer’s useful comments.

We recruited chronic disease patients from hospitals in a single geographic area in Taizhou, China. And the study population was selected on a convenient and voluntary basis. Therefore, there existed inevitable selection bias in this study.

We have revised in Discussion. Please see lines 344-346.

 

7.The authors do not propose a minimum sample size, what is the reference population? How large is it? It must be stated in the methods section Without the numerical identification of the reference population is not clear the validity of the study. A non-representative sample is by its self a non-sense-survey.

Response: Thanks for the reviewer’s useful comments.

Sample size determination using the G*Power software(ver. 3.1.9.7; Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany)[16,17].We used 2-sided testing, Odds ratio=2, Pr(Y=1| X=1) H0=0.5, α err prob=0.05, power (1-β err prob)=0.85,R2 other X=0.6.The minimum sample size was computed as 229.

We have revised in Study design and data collection. Please see lines 109-113.

 

8.Statistical analysis:

I suggest to insert a measure of the magnitude of the effect for the comparisons. Please consider to include effect sizes.

Response: Thanks for the reviewer’s useful comments.

The magnitude of the effect for the comparisons was measured by Gramer's V.

We have revised in Statistical analysis: and Table2. Please see lines 181-182.

 

Discussion:

9.I also suggest expanding. Emphasize the contribution of the study to the literature. The discussion must be updated with the discussion regarding the relation between knowledge and acceptance in different counties, a paragraph should be added with a proper reference (see the above mentioned reference).

Response: Thanks for the reviewer’s useful comments.

A comparison of the willingness of older adults with chronic diseases to receive the booster dose and its associated factors with the existing studies (Table4) of the primary doses for the general elderly revealed that the willingness of older adults in different countries ranged from 43.9% to 92.7%, and the results of our study showed that age groups >60 years with chronic diseases also had a high rate of willingness to receive the COVID-19 vaccine booster (77.9%), similar to their willingness to receive the primary dose (77.6%). In an Italian study, the elderly showed well knowledge about COVID-19 and its preventive aspects[29].The perceptions of the COVID-19 vaccine, particularly safety and efficacy, were positively associated factors in the willingness to receive the initial dose in the general elderly population in various countries .Our study found that willingness to receive a booster dose in the elderly chronic disease pa-tient population was similarly influenced by perceptions of COVID-19 vaccine safety and efficacy.

We have revised in Discussion and Table4. Please see lines 279-290 and Table4.

 

10.The Authors should add more practical recommendations for the reader, based on their findings.

Response: Thanks for the reviewer’s useful comments.

There are some practical recommendations based on this study. First, hospitals can provide individualized health education according to the different conditions of patients. Focus on health education for elderly people with stable chronic disease con-ditions and urge them to get booster vaccinations as soon as possible. And for patients whose condition is in an unstable stage, the main focus is on treating the disease. Sec-ondly, the government can develop incentives and establish cooperation with hospitals to precisely intervene in people who are suitable for COVID-19 booster vaccination.

We have revised in Discussion. Please see lines 334-340.

 

11.Also, the section of limitations and future search is also very short, the Authors could elaborate on that.

Response: Thanks for the reviewer’s useful comments.

There are some limitations to our study. First, we recruited chronic disease patients from hospitals in a single geographic area in Taizhou, China. And the study population was selected on a convenient and voluntary basis. Therefore, there existed in-evitable selection bias in this study. Second, The survey was conducted using a non-standard questions. Since our questionnaire uses a non-scale format, it is difficult to test the reliability, intelligibility and validation indexes. Third, patients' stability of chronic diseases was assessed by their self-assessment and it was measured by a sin-gle-choice question. Moreover, the evaluation criteria for disease stability vary among chronic diseases. Therefore, there may exist some measurement bias in the results of stability of chronic diseases. Fourth, our study did not analyze the elderly group with specific diseases, which is the direction of our follow-up-study.

We have revised in Discussion. Please see lines 343-353.

Author Response File: Author Response.pdf

Reviewer 3 Report

In this manuscript titled “Willingness to receive a booster dose of inactivated coronavirus disease 2019 vaccine among older adults with chronic diseases in Taizhou, China”, the authors used questionnaire to investigate the willingness to receive the COVID-19 vaccine booster in elder population with chronic diseases. And the authors found that the willingness to receive the booster is the same as that to receive the primary doses in this population. The authors also found certain factors were associated with a higher willingness to received the booster. Overall, this is an interesting and timely study. However, the authors didn’t clearly introduce what has been done in previous similar studies, so I don’t know how this study contributes to the overall field and whether there is any novelty in this study. Therefore, a major revision is needed.

 

Major issue:

 

1. Line 58-59, “To our knowledge, no existing studies have investigated the propensity to receive 58 COVID-19 vaccine boosters in elderly populations with chronic diseases”, this is an over-simplification of the previous studies. Table 4 clearly listed more than a dozen studies on the willingness to receive COVID vaccines in elder population. The authors need to clearly introduce what was known in these studies regarding this topic. For example, did previous studies have any information about whether any of the subjects received any COVID boosters? Did previous studies contain any information about whether any of the subjects were undergoing any kinds of chronic diseases? Did other researchers only use questionnaire to perform such studies on willingness to received COVID vaccines in elder population? Without the detailed background information, I don’t know whether this study has any novelty compared to the previous studies.

 

2. The authors found that “Stability of chronic diseases ” was associated with willingness to receive the booster in this population. How was stability of chronic diseases defined? Was this done through questionnaire too? Did patients or doctors determine the status of the stability? We are talking about a dozen of different chronic diseases, how did authors ensure that stability means the same status across different diseases? These details need to be clarified in method section.

Author Response

Reviewer3:

In this manuscript titled “Willingness to receive a booster dose of inactivated coronavirus disease 2019 vaccine among older adults with chronic diseases in Taizhou, China”, the authors used questionnaire to investigate the willingness to receive the COVID-19 vaccine booster in elder population with chronic diseases. And the authors found that the willingness to receive the booster is the same as that to receive the primary doses in this population. The authors also found certain factors were associated with a higher willingness to received the booster. Overall, this is an interesting and timely study. However, the authors didn’t clearly introduce what has been done in previous similar studies, so I don’t know how this study contributes to the overall field and whether there is any novelty in this study. Therefore, a major revision is needed.

Major issue:

1.Line 58-59, “To our knowledge, no existing studies have investigated the propensity to receive 58 COVID-19 vaccine boosters in elderly populations with chronic diseases”, this is an over-simplification of the previous studies. Table 4 clearly listed more than a dozen studies on the willingness to receive COVID vaccines in elder population. The authors need to clearly introduce what was known in these studies regarding this topic. For example, did previous studies have any information about whether any of the subjects received any COVID boosters? Did previous studies contain any information about whether any of the subjects were undergoing any kinds of chronic diseases? Did other researchers only use questionnaire to perform such studies on willingness to received COVID vaccines in elder population? Without the detailed background information, I don’t know whether this study has any novelty compared to the previous studies.

Response: Thanks for the reviewer’s useful comments. 

There are few studies on willingness to receive COVOD-19 vaccine booster that focus on the population of older adults with chronic diseases, mostly the general adult population and healthcare workers. Questionnaires have also been widely used as a research method in previous studies on the intention to vaccinate the elderly with the initial doses of the COVID-19 vaccine. The existing study has shown that bad health conditions can reduce the willingness of older adults to receive the initial dose of COVID-19 vaccine.

We have revised in Introduction. Please see lines 88-94.

2. The authors found that “Stability of chronic diseases” was associated with willingness to receive the booster in this population. How was stability of chronic diseases defined? Was this done through questionnaire too? Did patients or doctors determine the status of the stability? We are talking about a dozen of different chronic diseases, how did authors ensure that stability means the same status across different diseases? These details need to be clarified in method section.

Response: Thanks for the reviewer’s useful comments.

Patients' stability of chronic diseases was assessed by their self-assessment and it was measured by a single-choice question. Moreover, the evaluation criteria for disease stability vary among chronic diseases. Therefore, there may exist some measurement bias in the results of stability of chronic diseases. 

We have revised in Method and Discussion. Please see lines 155-156 and lines 348-352.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

the paper was improved and it is now suitable for publication

Reviewer 3 Report

All concerns resolved.