Neutralizing antibodies against SARS-CoV-2 variants of concern elicited by the Comirnaty COVID-19 vaccine in nursing home residents

Immunosenescence may impact the functionality and breadth of vaccine-elicited humoral immune responses. The ability of sera to neutralize the SARS-CoV-2 spike protein (S) from Beta, Gamma, Delta, and Epsilon variants of concern (VOCs) relative to the ancestral Wuhan-Hu-1 strain was compared in Comirnaty COVID-19-vaccinated elderly nursing home residents (n=30) or younger individuals (n=18) and non-vaccinated individuals who recovered from severe COVID-19 (n=19). In all groups, some participants lacked NtAb against one or more VOCs, mainly the Beta variant (15-20%). Serum NtAb titers were lowest against the Beta variant followed by Gamma, Epsilon, and Delta variants. Fold change reduction in NtAb titers relative to the ancestral strain was greatest for the Beta variant (6.7-18.8) followed by Gamma (3.6-6.2), Epsilon (2.9-5.8), and Delta (3.5-4.3) variants, regardless of the study group considered. In summary, older age, frailty, and concurrence of co-morbidities had no impact on the serum NtAb activity profile against SARS-CoV-2 VOCs.