Changing in adaptive cellular repertoire after different SARS-CoV-2 VOCs infection in a cohort of vaccinated Healthcare workers

Despite currently approved vaccines are highly effective in protecting against hospitalization and severe Covid-19 infections, however, their effectiveness in counteracting symptoms presentation and breakthrough infections appears to decrease over time. How pre-existing immunity responds to new variants with mutated antigens is a crucial information to elucidate the functional interplay between antibodies, B and T cell responses during infection with new SARS-CoV-2 variants. In this study, we monitored the dynamics and persistence of the immune response versus different SARS-CoV-2 variants of concern emerged during the pandemic period (2021-2022), in a cohort of vaccinated health care workers, who experienced breakthrough infection in the Pre-Delta, Delta and Omicron waves. Our results suggest a direct dependence between VOCs and different humoral and B and T cells balance in the post-infection period, despite the administration of a different number of vaccine doses and the elapsed time since the last vaccination.