Abstract
We aimed to investigate neutralizing antibody titers (NtAbT) to the P.1 and B.1 SARS-CoV-2 variants in a cohort of healthy health care workers (HCW), including 20 previously infected individuals tested at baseline (BL(inf), after a median of 298 days from diagnosis) and 21 days after receiving one vaccine dose (D1(inf)) and 15 uninfected subjects tested 21 days after the second-dose vaccination (D2(uninf)). All the subjects received BNT162b2 vaccination. D1(inf) NtAbT increased significantly with respect to BL(inf) against both B.1 and P.1 variants, with a fold-change significantly higher for P.1. D1(inf) NtAbT were significantly higher than D2(uninf) NtAbT, against B.1 and P.1. NtAbT against the two strains were highly correlated. P.1 NtAbT were significantly higher than B.1 NtAbT. This difference was significant for post-vaccination sera in infected and uninfected subjects. A single-dose BNT162b2 vaccination substantially boosted the NtAb response to both variants in the previously infected subjects. NtAb titers to B.1 and P.1 lineages were highly correlated, suggesting substantial cross-neutralization. Higher titers to the P.1 than to the B.1 strain were driven by the post-vaccination titers, highlighting that cross-neutralization can be enhanced by vaccination.