Abstract
Background: This study aims to investigate the extent of the BNT162b2 mRNA vaccine-induced antibodies against SARS-CoV-2 in a large cohort of Italian subjects belonging to the early vaccinated cohort in Italy. Methods: A prospective study was conducted between December 2020 and May 2021. Three blood samples were collected for each participant: one at the time of the first vaccine dose (T0), one at the time of the second vaccine dose, (T1) and the third 30 days after this last dose (T2). Results: We enrolled 2591 fully vaccinated subjects; 16.5% were frail subjects, and 9.8% were over 80 years old. Overall, 98.1% of subjects were seropositive when tested at T2, and 76.3% developed an anti-S IgG titer ≥4160 AU/mL, which is adequate to develop viral neutralizing antibodies. Seronegative subjects at T1 were more likely to remain seronegative at T2 or to develop a low–intermediate anti-S IgG titer (51–4159 AU/mL). Conclusions: In summary, vaccination leads to detectable anti-S IgG titer in nearly all vaccine recipients. Stratification of the seroconversion level could be useful to promptly identify high-risk groups who may not develop a viral neutralizing response, even in the presence of seroconversion, and therefore may remain at higher risk of infection, despite vaccination.
Highlights
A new acute respiratory syndrome, coronavirus disease 2019 (COVID-19), emerged from the region of Wuhan, China in December 2019
The results of this prospective study provide real-world data demonstrating that the BNT162b2 mRNA vaccine has induced seroconversion in the majority of a large cohort of vaccine recipients who may not participate in clinical trials
We found that the only predictor of the seroconversion after the full course of vaccination was the anti-S IgG titer measured at T1
Summary
A new acute respiratory syndrome, coronavirus disease 2019 (COVID-19), emerged from the region of Wuhan, China in December 2019. The causative pathogen was subsequently identified as the severe acute respiratory syndrome related coronavirus 2 (SARSCoV-2) [1], with severe morbidity and mortality rates [2,3]. This virus, recognized as the etiologic agent of COVID-19 disease, is the seventh known coronavirus to infect humans [4]. 98.1% of subjects were seropositive when tested at T2, and 76.3% developed an anti-S IgG titer ≥4160 AU/mL, which is adequate to develop viral neutralizing antibodies. Stratification of the seroconversion level could be useful to promptly identify high-risk groups who may not develop a viral neutralizing response, even in the presence of seroconversion, and may remain at higher risk of infection, despite vaccination
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
