LAUSR

The immune factors associated with impaired SARS-CoV-2 vaccine response in the elderly are mostly unknown. We studied old and young people vaccinated with SARS-CoV-2 BNT162b2 mRNA before and after the first and second dose. Aging was associated with a lower anti-RBD IgG levels and a decreased magnitude and polyfunctionality of SARS-CoV-2 specific T cell response. The dramatic decrease in thymic function in the elderly, which fueled alteration in T cell homeostasis, and lower CD161+ T cell levels were associated with decreased T cell response two months after vaccination. Additionally, a deficient dendritic cell (DC) homing, activation and Toll like receptor (TLR)-mediated function, along with a proinflammatory functional profile in monocytes, were observed in the elderly, which was also related to lower specific T cell response after vaccination. These findings might be relevant for the improvement of the current vaccination strategies and for the development of new vaccine prototypes.