B and T cell immune responses elicited by the BNT162b2 (Pfizer BioNTech) COVID-19 vaccine in nursing home residents

Torres, I.; Albert, E.; Gimenez, E.; Alcaraz, M. J.; Botija, P.; Amat, P.; Remigia, M. J.; Beltran, M. J.; Rodado, C.; Huntley, D.; Olea, B.; Navarro, D.

Objectives: The immunogenicity of the BNT162b2 COVID-19 vaccine is understudied in elderly people with comorbidities. We assessed SARS-CoV-2-S-targeted antibody and T cell responses following full vaccination in nursing home residents (NHR). Methods: We recruited 60 NHR (44 female; median age, 87.5 years), of whom 10 had previously had COVID-19, and 18 healthy controls (15 female; median age, 48.5 years). Pre- and post-vaccination blood specimens were available for quantitation of total antibodies binding RBD and enumeration of SARS-CoV-2-S-reactive IFN-{gamma}; CD4+ and CD8+ T cells by flow cytometry. Results: The seroconversion rate in presumably SARS-CoV-2 naive NHR (95.3%), either with or without comorbidities, was similar to controls (94.4%). A robust booster effect was documented in NHR with prior COVID-19. Plasma antibody levels were higher in convalescent NHR than in individuals across the other two groups. A large percentage of NHR had SARS-CoV-2 S-reactive IFN-{gamma}; CD8+ and/or CD4+ T cells at baseline, in contrast to healthy controls. Either CD8+ and/or CD4+ T-cell responses were documented in all control subjects after vaccination. Contrariwise, the percentage of NHR exhibiting detectable SARS-CoV-2 IFN-{gamma}; CD8+ or CD4+ T-cell responses (or both), irrespective of their baseline SARS-CoV-2 infection status, dropped consistently after vaccination. Overall, SARS-CoV-2 IFN-{gamma}; CD8+ and CD4+ T-cell responses in NHR decreased in post-vaccination specimens. Conclusion: The BNT162b2 COVID-19 vaccine elicits robust SARS-CoV-2-S antibody responses in NHR. Nevertheless, the frequency and magnitude of detectable SARS-CoV-2 IFN-{gamma}; T-cell responses after vaccination was lower in NHR compared to controls.