Assessment of the Humoral Immune Response Following COVID-19 Vaccination in Healthcare Workers: A One Year Longitudinal Study

Round 1

Reviewer 1 Report

The aim of the study was to investigate in HCW during a 12 months' prospective longitudinal observational study the humoral immune response one year after SARS-CoV-2 mRNA vaccination in correlation to host factors such as gender, age, comorbidities, BMI and previous SARS-CoV-2 infections.

Data are supported by a rigorously performed statistical analysis which is well represented in the several Figures.  

Author Response

Thank you for the careful assessment of our manuscript and acceptance in the current form.

Reviewer 2 Report

This manuscript reported by Ruta et al. is to evaluate the dynamics and persistence of the humoral immune response in health-care workers (HCW) during one year after anti-COVID-19 vaccination with or without a booster shot. The contribution of host factors, such as gender, age, comorbidities, BMI, and previous SARS-CoV-2 infection, which may influence the immune response, is also assessed. The level of antibodies was measured, which included detection of anti-spike (S)/receptor binding domain (RBD), IgG antibodies against the nucleocapsid protein (NCP), and IgA antibodies against the spike protein. Additionally, the antibodies’ neutralizing capacity was assessed by use of a surrogate SARS-CoV-2 virus neutralization test. Regarding to the selected samples, the participants were recruited from four hospitals in Romania. They have been vaccinated with two doses of the BNT162b2 mRNA vaccine (Pfizer-BioNTech) at the time of enrollment. Out of the 945 participants, 571 individuals had at least two adequate blood samples collected for analysis. Venous blood samples were collected at 1 month, 3 months, 6 months, 9 months, or 12 months after the second dose. Prior to 9 months, about 70% of the participants received a third dose of BNT162b2 mRNA vaccine (Pfizer-BioNTech). 

The authors found that there was a constant decline for participants in the level of anti-S/RBD antibody, followed by a transient increase after a booster shot during one year after vaccination. Then the antibody levels were still waning post-booster. However, individuals with prior SARS-CoV-2 infection developed higher levels of IgG antibodies and long-lasting IgA antibodies after a booster shot in comparison with the uninfected. Moreover, 68.20% of HCW was found to preserve the neutralization capacity against the ancestral variant and 17.08% against the Omicron variant. Breakthrough infections were present in 6.65% of all participants and found there was no correlation with the previous level of anti-S/RBD and IgG.

Overall, the content in this manuscript is well presented. It reveals important information about the immune response after COVID-19 vaccination with a mRNA vaccine. Quality and importance of this manuscript reach the standard of Biomedicines for its publication. However, a paragraph of limitations and recommendations is suggested to be separately added after the Discussion. Some minor points have to be clarified and revised.

❅  The samples were all taken from health care workers. The population of age 35-50 took up about 47.8% in this study. Because of the limitation of the samples selected from a particular workforce, there is an obvious bias of ages, especially for the age over 65 and age under 18. The elderly (>65) is the most vulnerable group. Thus their immune response following anti-COVID-19 vaccination is quite critical as severe disease can occur to them more easily. Additionally, the recent Omicron variant is prone to attack youngsters, especially children. Both points are worthy of discussion in the limitations and recommendations.

❅  In this manuscript, the results described in “3.3 Breakthrough infections data” are of importance. However, Figure 2 is unclear and difficult to follow by the readers. What are INF and ReINF? The infection (prior or post vaccine) and reinfection results from the same or different SARS-CoV-2 viral variants? Why there are four stars (****) in the figure and three stars (***) in its legend? Additionally, “Figure 2” is missing in the description and needs to be added.

After these modifications are made, this manuscript deserves quick publication in Biomolecules.

Comments for author File: Comments.docx

Author Response

Point 1:  The samples were all taken from health care workers. The population of age 35-50 took up about 47.8% in this study. Because of the limitation of the samples selected from a particular workforce, there is an obvious bias of ages, especially for the age over 65 and age under 18. The elderly (>65) is the most vulnerable group. Thus their immune response following anti-COVID-19 vaccination is quite critical as severe disease can occur to them more easily. Additionally, the recent Omicron variant is prone to attack youngsters, especially children. Both points are worthy of discussion in the limitations and recommendations.

We thank the reviewer for the helpful suggestion. We have included further comments on our study limitations (found at the end of discussions section). More specifically, the age bias and importance of the infected variants is discussed:

There is a certain age bias, since more than 47% of the individuals enrolled in the study were aged 35-50 years, while the most vulnerable age group, persons >65 years, who might have a less robust immune response due to immunesenescence, are under-represented (only 2.4% of the study subjects). Yet, the enrolled population is representative for the age structure of the health care work force in Romania, and the dynamic of the immune response is relevant for further specific recommendations in the national vaccination strategy. The study stopped during the initial phase of the Omicron wave in Romania, in which most infections were registered in children and young adults, it is probable that many more reinfections with the highly transmissible and antigenically unrelated Omicron variant will be recorded during the next months in health care workers too.

 

Point 2:  In this manuscript, the results described in “3.3 Breakthrough infections data” are of importance. However, Figure 2 is unclear and difficult to follow by the readers. What are INF and ReINF? The infection (prior or post vaccine) and reinfection results from the same or different SARS-CoV-2 viral variants? Why there are four stars (****) in the figure and three stars (***) in its legend? Additionally, “Figure 2” is missing in the description and needs to be added.

Thank you for your comment. We have added the description of figure 2 in text and corrected the number of stars in the figure. Additionally, we edited the legend for more clarity and included some details in the manuscript body. We hope that now the figure is easier to follow.