Immune Response to BNT162b2 mRNA COVID-19 Vaccine in a Cohort of Healthcare Workers.

In this 13-month follow-up study, we examined a cohort of vaccinated healthcare workers without prior SARS-CoV-2 infection to assess the humoral and cellular response to the BNT162b2 mRNA COVID-19 vaccine over time. We measured median immunoglobulin G and lymphocyte subpopulation levels after the first and second doses, at five months post-second dose, and before and after the third dose. Our findings evinced a remarkable initial cellular and humoral response to each vaccine dose, although a progressive decline suggests the potential need for long-term booster doses. Age analysis showed significantly higher immunoglobulin G levels in the younger group after the first dose administration, although these differences were not maintained in the following doses. Preserving cellular immunity could assure long-lasting protection against SARS-CoV-2 infection.