COVID-19 mRNA BNT162b2 vaccine safety and antibodies level among healthcare workers at Centre Hospitalier du Nord

Studying the levels of the anti-spike protein receptor-binding domain (S-RBD) antibodies as well as the vaccine safety is very important to evaluate the protection level against the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV2) infection and to motivate individuals to receive the vaccine. In this study, we evaluate the effect of the mRNA BNT162b2 vaccine using the EUROIMMUN anti-SARS-CoV-2 ELISA (IgG) for the measurement. We detected the IgG class antibodies to SARS-CoV-2 in the human serum, or plasma, of 217 eligible participants aged >18 years, recruited between March and June 2021. These participants were divided into 2 groups: the first group consisted of 149 participants without prior infection, while the second group included 68 participants who had recovered from symptomatic and asymptomatic COVID-19 infections. All the adverse effects were minor local or systematic reactions such as local pain, asthenia, body ache, muscle pain and headache. The level of the adverse effects increased following the second vaccine dose. The adverse effects were higher in participants with previous symptomatic SARS-CoV2 infection (p=0.020). This was due to the presence of anti-S-RBD IgG levels before the vaccination. Moreover, the adverse effects were higher in females than males after the first dose (p=0.025) and the second dose (p=0.01). As for the anti-S-RBD IgG levels, they were all positive at the end of the second dose. The anti-S-RBD IgG levels 21 days after the vaccination dose were higher than the pre-vaccination levels (p=0.000) and they were higher in previously infected participants before getting the first dose (p=0.000). Our results show a good antibody response at the end of the two mRNA BNT162b2 vaccine doses in both previously infected and not infected participants. Moreover, our study highlighted the minor adverse effects reported following each dose.