Immunogenicity and safety of the BNT162b2 mRNA COVID-19 vaccine in healthcare workers

Abstract

Introduction: The coronavirus disease 2019 (COVID-19) pandemic caused global public health and economic crises. Objective: The aim of this observation study was to estimate the effectiveness, safety and elicited immune response of the BNT162b2 mRNA Pfizer-BioNTech vaccine in healthcare workers of the Buda Hospital of the Hospitaller Order of St. John of God. Method: After vaccination, the infection rate, adverse events and the kinetics of anti-SARS-CoV-2 spike (S) protein and anti-SARS-CoV-2 nucleocapsid (N) protein antibodies were evaluated. Results: Before vaccination, from the 295 healthcare workers 36 recovered from prior COVID-19 infection (COVID-19-positive group). After the second vaccination, there was no COVID-19 infection during the three-month follow-up period. The adverse events were mild. In the COVID-19-positive group, the median cut-off index of anti-N antibodies measured at 4 weeks after the first vaccination were significantly (p<0.0001) higher (28.37) than in the COVID-19-negative group (0.085). After the first vaccine, the median titer of anti-S antibodies was significantly higher (p<0.0001) in the COVID-19-positive group (8015 U/ml) compared to the COVID-19-negative group (23.18 U/ml). In the COVID-19-negative group, the median titer of anti-S antibodies increased significantly (p<0.0001) after the second vaccine (from 23.18 U/ml to 1173 U/ml), showing an increase of 500×. Conclusions: After the second vaccination, there was no COVID-19 infection during the follow-up. In the COVID-19-negative group, the anti-S antibody titer is moderate after the first vaccination and increases significantly after the second vaccine. In the COVID-19-positive group, the first vaccine induces significant anti-S antibody production.