Assessment of SARS-CoV-2 Infection, Vaccination, and Immunity Status Among a Population of Dentists/Academic Professors in a Clinical Setting: One-Year Findings

Round 1

Reviewer 1 Report

 

The manuscript Assessment of SARS-CoV-2 Exposure, Vaccination and Immunity Status among a population of Dentists/Academic Professors in a Clinical Setting: One-year Findings" presents a cross-sectional study conducted among 47 dental professionals and academic professors at University Fernando Pessoa, aiming to assess SARS-CoV-2 exposure, vaccination status, and humoral immunity (IgM and IgG antibody levels) at two time points: July 2021 and June 2022. The study uses serological testing (ELISA) and participant self-reported data to evaluate associations between immunity, demographics, and vaccination/infection history. The authors report high vaccination and seropositivity rates, and identify a significant association between IgG positivity and both age (<50 years) and number of vaccine doses received.

Although this study addresses a timely topic there are multiple issues which should be addressed to make this study robust and concise. Thus, the following points should be tackled:

 

• The study is incorrectly described as a "prospective" protocol. So were data collected at only two distinct time points with no actual follow-up in between. A true prospective design would require continuous or repeated measures per participant across time.
• What is the power of this study? The small sample size (N=47) could sever the study's statistical power, reducing the reliability of inferential conclusions. Given the wide age range and heterogeneity of the sample, subgroup analyses are particularly underpowered.
• What are the measures to selection bias? Recruitment was voluntary and limited to professionals affiliated with a single institution. This hinders the generalizability of findings to broader academic or clinical populations.
• What is the control group? Without a non-dental or general population comparator, it is difficult to assess the occupational risk or serological profile's uniqueness in this cohort.
• How did the authors control reliance on self-report for infection history and recall bias?
• Independent medical verification? Please comment in the methods and discussion section on this as well.
• There is insufficient clarity on whether reported infections were symptomatic, confirmed by testing, or based on personal assumption.
• The ELISA assay’s threshold of ≥1 AU/mL for positivity is used without referencing standardization (e.g., WHO IU/mL), limiting comparability. The term "seropositivity" is used imprecisely throughout.
• The correlation with clinical outcomes is missing.
• The use of terminology is confusing.
• Tables are cluttered, with redundant or unclear stratifications that hinder interpretation rather than aid it.
• The manuscript would benefit from language editing for clarity and conciseness.
• The introduction is overly long and should be condensed to better focus on the rationale for studying this specific population.

 

• The study is incorrectly described as a "prospective" protocol. So were data collected at only two distinct time points with no actual follow-up in between. A true prospective design would require continuous or repeated measures per participant across time.
• What is the power of this study? The small sample size (N=47) could sever the study's statistical power, reducing the reliability of inferential conclusions. Given the wide age range and heterogeneity of the sample, subgroup analyses are particularly underpowered.
• What are the measures to selection bias? Recruitment was voluntary and limited to professionals affiliated with a single institution. This hinders the generalizability of findings to broader academic or clinical populations.
• What is the control group? Without a non-dental or general population comparator, it is difficult to assess the occupational risk or serological profile's uniqueness in this cohort.
• How did the authors control reliance on self-report for infection history and recall bias?
• Independent medical verification? Please comment in the methods and discussion section on this as well.
• There is insufficient clarity on whether reported infections were symptomatic, confirmed by testing, or based on personal assumption.
• The ELISA assay’s threshold of ≥1 AU/mL for positivity is used without referencing standardization (e.g., WHO IU/mL), limiting comparability. The term "seropositivity" is used imprecisely throughout.
• The correlation with clinical outcomes is missing.
• The use of terminology is confusing.
• Tables are cluttered, with redundant or unclear stratifications that hinder interpretation rather than aid it.
• The manuscript would benefit from language editing for clarity and conciseness.
• The introduction is overly long and should be condensed to better focus on the rationale for studying this specific population.

Author Response

Please see the attachment with the answer to your comments. 

Author Response File: Author Response.pdf

Reviewer 2 Report

Here, authors investigated the prevalence of SARS-CoV-2 "exposure" and/or vaccination in a cohort of dentists and university professors. Using ELISA, the authors have measured the antibody levels of anti-S1-RBD IgM and IgG from samples obtained at two time points a year apart. Further, authors aimed to determine possible association between prevalence of SARS-CoV-2 "exposure" and vaccination status with participants demographics.

I have some major comments on this study that I believe should generally be considered in any scientific studies to properly convey the message of that study. 

1- The authors loosely use the term " exposure" and "infection" within this study. The term "exposure" can refer to individuals who were in contact with the SARS-CoV-2 virus such as interacting with Covid patients thus having exposure! It seems that the authors consider exposure equal to infection! If so, the term exposure is not the right term to be used here. If not, what's the self-defined criteria for exposure to the virus? This needs to be clarified through the paper. 

2- The authors have used ELISA to measure the IgM and IgG levels within the samples. However, there is no section explaining the ELISA method including proper controls and standards, number of technical replicates used for the measurements as well as normalization of results based on variations between different time points the experiment was conducted! These are all very important for drawing any conclusions as this assay is the basis of the other conclusions within the paper.

3- Further, authors used the threshold of 1 Au/ml to consider if a sample is positive or negative for IgM or IgG. This threshold is pretty low and various other similar studies including : "Interpretations of SARS-CoV-2 IgM and IgG antibody titers in the seroepidemiological study of asymptomatic healthy volunteers" (https://www.sciencedirect.com/science/article/pii/S1341321X21003317 ), "Dynamic changes of serum SARS-CoV-2 antibody levels in COVID-19 patients" ( https://pmc.ncbi.nlm.nih.gov/articles/PMC9021032/) and "Clinical significance of serum IgM and IgG levels in COVID-19 patients in Hubei Province, China" (https://pmc.ncbi.nlm.nih.gov/articles/PMC8487787/ ) consider 5 or 10 Au/ml as the lowest threshold. Using such low arbitrary threshold is damaging the credibility of their presented results. For example, how would the results look if the threshold of 10 Au/ml is considered?

4- As mentioned by the authors themselves, the number of participants in the study is too small to really deduct any significant conclusions and I am afraid such work needs a really higher number of participants. Further, frequency of vaccinations, type of vaccines (for e.g. mRNA vaccine, attenuated virus, etc., ) each individual received can further complicate the level of antibodies within each patient thus making it very difficult for any conclusion in regards to association between seropositivity and participants' demographics.

5- Moreover, level of measured IgM is very low even amongst individuals who received vaccine a month prior to collection of samples? IgM level normally should be stable up to 30-35 days after infection or vaccination. I wonder what authors think of such low values. This once again shows the importance of including positive control to show that anti-IgM antibody functions properly.

Due to the above mentioned comments, I unfortunately do not see this work ready for publication yet. These are major concerns that needs to be properly addressed before publication. 

There are various minor mistakes through the paper such as wrong terms or grammatical issues which need to be corrected such as: in line 344 "of" needs to be changed to "from", in line 47 "contracting" needs to be changed to "contacting", there is an extra space in line 72 and etc.

Author Response

Please see the attachment with the reply to your comments

Author Response File: Author Response.pdf

Reviewer 3 Report

This is a straightforward survey and mostly descriptive analysis. The 47 respondents used in the analysis are a subset of an initial 62 potential respondents. Is there any evidence to suggest that the sample is biased and not  representative of the population chosen? For reference see lines 350 and 351.

Table 1 reports that there are no significant associations. If so, I question the value of its inclusion. However, a table for just the descriptive statistics is necessary. (Note: at the bottom of Table 1 reference is made to the “Qui-square test” which should be Chi-square)

Overall, Tables 2 and 3 provide interesting information about exposure and vaccine status as does Table 4 with additional statistical tests.

Limitations of the study are effectively summarized as are the suggestions for future research.

I am somewhat confused by the Discussion section. Some material would be better included in the Introduction.  For example, the passage that “healthcare professionals are considered a risk group” should be mentioned in the Introduction. I encourage the authors to refocus and reorganize the discussion with a succinct focus on the descriptive tables 1, 2 and 3 and then additional commentary on the implications for Table 4.

T

NA

Author Response

Please see the attachment with the reply to your comments

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Congrats. All points are sufficiently addressed.

Congrats. All points are sufficiently addressed.

Reviewer 3 Report

Thanks to the authors for their reply to my comments.

None