Determinants of COVID-19 and Influenza Vaccination Among People with Diabetes Mellitus in Primary Health Care

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Considering that most people with diabetes mellitus have a compromised immune system that puts them at risk of infections, this study is relevant to healthcare providers, policymakers, program managers, and the general public. The title reflects the content of the manuscript. The abstract is an adequate summary of the manuscript. The introduction orients the readers to the topic, identifies a gap in literature, and states the aim of the study. The materials and methods section is adequately described to allow for the replication of the study. The narrative sections of the results should be improved. In the discussion section, some of the results were not compared with previous literature. The authors acknowledge the limitations of their study. The recommendations and conclusion are based on the findings of the study.

MAJOR REVISIONS

Abstract

1. The software used for data analysis should be stated.

Materials and methods

2. Information on the reliability and validity of the questionnaire should be provided.

Results

3. In lines 199-201, provide the 95% confidence intervals of COVID-19 and influenza vaccination rates.
4. In lines 229-230, the authors state, ‘Additionally, higher adherence to influenza vaccination and lower adherence to pneumococcal vaccination were observed (Table 3).’ Do the authors mean COVID-19 instead of pneumococcal?
5. In lines 263-277, the adjusted odds ratios, together with their 95% confidence intervals, should be presented in brackets for the mentioned variables.

Discussion

6. In lines 319-325, 327-333, 334-338, 340-346, and 347-350, the authors should compare their results with those of previous studies before they try to explain the findings.

MINOR REVISIONS

1. In Lines 90-91, the authors state, ‘Furthermore, it is assumed that socioeconomic, cultural, behavioral, and clinical determinants are associated with vaccination adherence.’ The authors should provide a reference to this statement.
2. e-SUS in line 105 should be written in full.
3. In Table 1, the authors should leave space after each variable group for readers to see clearly where each group ends.

Author Response

Dear Reviewer,

We thank you for your careful review of our manuscript and for the valuable suggestions provided. All recommendations were carefully considered and incorporated into the revised version of the manuscript. The corresponding changes have been highlighted in the revised file.

Below, we provide a point-by-point response to the issues raised. We remain at your disposal for any further clarification.

1. Abstract

• The software used for data analysis should be stated.

The Abstract section has been revised to include the name and version of the statistical software used for data analysis.

2. Introdution

 In Lines 90-91, the authors state, ‘Furthermore, it is assumed that socioeconomic, cultural, behavioral, and clinical determinants are associated with vaccination adherence.’ The authors should provide a reference to this statement.

The sentence referred to the study's underlying hypothesis that socioeconomic, cultural, behavioral, and clinical determinants may be associated with vaccination adherence among individuals with diabetes. Nevertheless, we agree that this assumption should be supported by the literature. Therefore, we have added two relevant references that provide evidence for the influence of these determinants on vaccination uptake, and the text has been revised accordingly 

3. Materials and methods

• Information on the reliability and validity of the questionnaire should be provided.

The questionnaire was developed by the research team based on the study objectives and relevant literature. Content validity was established through review and consensus among researchers and experts in vaccination and public health regarding the relevance, clarity, and adequacy of the instrument items. In addition, a pilot study was conducted with a separate sample (n = 15) to assess question comprehension and instrument operationalization. Based on the pilot study, minor semantic adjustments were made without structural or conceptual modifications. This information has now been added to the Methods section to clarify the questionnaire development and validation process.

• e-SUS in line 105 should be written in full.

The acronym has been defined in full at its first mention in the manuscript to improve clarity for international readers who may not be familiar with the Brazilian health information system

• In Table 1, the authors should leave space after each variable group for readers to see clearly where each group ends.

To improve the readability of Table 1 and facilitate the visualization of the different variable groups, separator lines have been inserted between the groups in the table.

4. Results 

• In lines 199-201, provide the 95% confidence intervals of COVID-19 and influenza vaccination rates.

The 95% confidence intervals for COVID-19 and influenza vaccination rates have been added to the Results section to provide a measure of precision for the estimated vaccination coverage.

• In lines 229-230, the authors state, ‘Additionally, higher adherence to influenza vaccination and lower adherence to pneumococcal vaccination were observed (Table 3).’ Do the authors mean COVID-19 instead of pneumococcal?

We confirm that the original sentence contained an inconsistency. The text has been revised to ensure clarity and accuracy, now correctly distinguishing adherence to influenza, COVID-19, and pneumococcal vaccination.

• In lines 263-277, the adjusted odds ratios, together with their 95% confidence intervals, should be presented in brackets for the mentioned variables.

The adjusted odds ratios and their corresponding 95% confidence intervals have been added in the text for all variables mentioned in this section, improving the clarity and interpretation of the results.

5. Discussion 

• In lines 319-325, 327-333, 334-338, 340-346, and 347-350, the authors should compare their results with those of previous studies before they try to explain the findings.

The Discussion section was revised to strengthen the comparison between our findings and those reported in previous studies before presenting possible explanations for the observed associations. Specifically, we incorporated additional evidence from studies conducted in different countries and settings, including investigations involving individuals with diabetes and other chronic conditions, as well as findings from systematic and scoping reviews. These additions allowed us to contextualize our results regarding communication channels, alcohol consumption, duration of diabetes, medical follow-up, healthcare professional recommendations, and religious affiliation, highlighting both convergent and divergent findings reported in the literature. Only after establishing these comparisons did we expand the discussion of potential explanatory mechanisms and contextual factors underlying the observed associations.

Reviewer 2 Report

Comments and Suggestions for Authors

This study evaluated the various determinants of influenza and COVID-19 vaccination among patients with diabetes mellitus. The study was done well, but some issues need to be addressed to improve this work.
1. The first 3 paragraphs of the introduction (lines 55-70) should be shortened. I recommend removing the basic info on diabetes and move to its epidemiology in Brazil and then the impact of vaccine-preventable diseases (such as influenza and COVID-19) on patients with diabetes.
2. Lines 99-101: What about ethical approval?
3. Line 103: The citation here [30] is not for sampling process, so I think is irrelevant. Also and if relevant, it should be moved to the end of the sentence.
4. Line 195: The significance should be at P less than 0.05 and not less than or equal to 0.05. Please correct it here and also revise all your interpretations for statistical significance accordingly.
5. At which P value did you select variable for the multivariable model?
6. Table 2 and lines 213-217: Why are the P values < 0.2 in bold and stated in the results? The statistical analysis part of the methods states that significant is set at P < 0.05. Same for lines 233-239 with Table 3 and lines 253-259 with Table 4.

Author Response

Dear Reviewer,

 

We thank you for your careful review of our manuscript and for the valuable suggestions provided. All recommendations were carefully considered and incorporated into the revised version of the manuscript. The corresponding changes have been highlighted in the revised file.

 

Below, we provide a point-by-point response to the issues raised. We remain at your disposal for any further clarification.

 

• The first 3 paragraphs of the introduction (lines 55-70) should be shortened. I recommend removing the basic info on diabetes and move to its epidemiology in Brazil and then the impact of vaccine-preventable diseases (such as influenza and COVID-19) on patients with diabetes.

The Introduction was revised and shortened by removing detailed background information on the pathophysiology of diabetes mellitus. The text was reorganized to place greater emphasis on the epidemiology of diabetes in Brazil and on the increased susceptibility of individuals with diabetes to vaccine-preventable diseases and their complications. These modifications improved the focus and conciseness of the Introduction while preserving the key information and supporting references.

• Lines 99-101: What about ethical approval?

Information regarding ethical approval is provided in the Ethics Statement section at the end of the manuscript, in accordance with the journal's formatting and reporting guidelines

• Line 103: The citation here [30] is not for sampling process, so I think is irrelevant. Also and if relevant, it should be moved to the end of the sentence.

 We consider it important to retain reference [30], as the material available in this source provides a more comprehensive description of the sampling process adopted in the study. Due to manuscript length limitations, it was not possible to include all methodological details regarding the sampling procedure within the manuscript itself. Therefore, we believe that maintaining the reference may assist readers seeking additional information on this aspect. As suggested, the citation has been relocated to the end of the sentence.

• Line 195: The significance should be at P less than 0.05 and not less than or equal to 0.05. Please correct it here and also revise all your interpretations for statistical significance accordingly.

The significance level has been corrected from p ≤ 0.05 to p < 0.05 in the Methods section. In addition, we reviewed the manuscript to ensure that all interpretations and reporting of statistical significance are consistent with this criterion. These revisions did not affect the study findings or conclusions.

• At which P value did you select variable for the multivariable model?

Variables with a p-value < 0.20 in the bivariate analysis were selected for inclusion in the multivariable logistic regression models. This criterion was adopted to avoid the premature exclusion of potentially relevant variables and is commonly used in epidemiological studies. We have clarified this procedure in the Methods section.

• Table 2 and lines 213-217: Why are the P values < 0.2 in bold and stated in the results? The statistical analysis part of the methods states that significant is set at P < 0.05. Same for lines 233-239 with Table 3 and lines 253-259 with Table 4.

 The p-values highlighted in Tables 2, 3, and 4 and described in the corresponding Results sections do not represent statistically significant associations. Rather, they indicate variables that met the pre-established criterion (p < 0.20) for inclusion in the multivariable logistic regression models. The significance level for the final analyses remained p < 0.05, as described in the Methods section. To avoid misinterpretation, we revised the Methods section to explicitly clarify the use of the p < 0.20 threshold for variable selection. In addition, the Results section was revised to indicate that these variables met the criterion for inclusion in the multivariable models, rather than implying statistical significance. We also removed the bold formatting from p-values < 0.20 in Tables 2, 3, and 4, as this highlighting could be interpreted as indicating statistical significance. The corresponding table contents were updated accordingly.

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors, The manuscript is interesting, but requires minor revisions.

The following are some suggestions.

1) Was the questionnaire created by the researchers? Was it validated? If so, how? If not, why?

2) Did the authors attempt a stepwise regression? Were the results significantly different from those obtained in Table 5?

3) For Table 5, to demonstrate the model's goodness of fit, it would be appropriate to display the pseudo R^2.

4) It would be appropriate to supplement the conclusions by offering suggestions to policymakers for improving the situation.

Kind regards.

Author Response

Dear Reviewer,

 

We thank you for your careful review of our manuscript and for the valuable suggestions provided. All recommendations were carefully considered and incorporated into the revised version of the manuscript. The corresponding changes have been highlighted in the revised file.

 

Below, we provide a point-by-point response to the issues raised. We remain at your disposal for any further clarification.

 

• Was the questionnaire created by the researchers? Was it validated? If so, how? If not, why?

The questionnaire was developed by the research team based on the study objectives and relevant literature. Content validity was established through review and consensus among researchers and experts in vaccination and public health regarding the relevance, clarity, and adequacy of the instrument items. In addition, a pilot study was conducted with a separate sample (n = 15) to assess question comprehension and instrument operationalization. Based on the pilot study, minor semantic adjustments were made without structural or conceptual modifications. This information has now been added to the Methods section to clarify the questionnaire development and validation process.

• Did the authors attempt a stepwise regression? Were the results significantly different from those obtained in Table 5?

As an additional analysis, we performed stepwise logistic regression and observed results consistent with those presented in Table 5. The variables retained in the model remained the same, with only slight reductions in the odds ratios (ORs) and no meaningful changes in the p-values or in the statistical significance of the associations. Therefore, the stepwise procedure did not substantially alter the interpretation of the findings, supporting the robustness of the final model presented in the manuscript.

• For Table 5, to demonstrate the model's goodness of fit, it would be appropriate to display the pseudo R^2.

To provide additional information regarding model fit, we included the pseudo R² values for the final multivariable models of COVID-19 and influenza vaccination in the footnote of Table 5. We also added the overall significance of each model (p < 0.001). The COVID-19 vaccination model presented a pseudo R² of 0.10, while the influenza vaccination model presented a pseudo R² of 0.20. Although these values indicate a modest explanatory power, both models were statistically significant and provide valid evidence regarding the factors associated with vaccination status in the study population.

• It would be appropriate to supplement the conclusions by offering suggestions to policymakers for improving the situation.

We thank the reviewer for this valuable suggestion. We agree that the findings of this study have important implications for public health policy. Therefore, we revised the conclusion section to include recommendations for policymakers and health managers, emphasizing the development of targeted vaccination strategies for individuals with diabetes mellitus, the integration of vaccination assessment into routine healthcare encounters, and investments in health education and immunization information systems. These additions highlight the practical implications of our findings and their potential contribution to improving vaccination coverage among this high-risk population

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

I appreciate the revisions made by the authors and their appropriate responses to the comments. I have no further comments and I endorse the manuscript for publication.