B and T cell immune responses elicited by the Comirnaty® COVID-19 vaccine in nursing home residents

Torres, Ignacio; Albert, Eliseo; Giménez, Estela; Alcaraz, María Jesús; Botija, Pilar; Amat, Paula; Remigia, María José; Beltrán, María José; Rodado, Celia; Huntley, Dixie; Olea, Beatriz; Navarro, David

OBJECTIVES: The immunogenicity of the Comirnaty® COVID-19 vaccine is understudied in elderly people with comorbidities. SARS-CoV-2-S-targeted antibody and T cell responses following full vaccination were assessed in nursing home residents. METHODS: Sixty nursing home residents (44 female; age, 53-100 years), of whom 10 had previously been diagnosed of COVID-19, and 18 healthy controls (15 female; age, 27-54 years) were recruited. Pre- and post-vaccination blood specimens were available for quantitation of total antibodies binding SARS-CoV-2 S protein and enumeration of SARS-CoV-2-S-reactive IFN-γ CD4(+) and CD8(+) T cells by flow cytometry. RESULTS: The seroconversion rate in presumably SARS-CoV-2 naïve nursing home residents (41/43; 95.3%), was similar to controls (17/18; 94.4%). A booster effect was documented in post vaccination samples of nursing home residents with prior COVID-19. Plasma antibody levels were higher (P<0.01) in recovered nursing home residents (all 2,500 IU/ml) than in individuals across the other two groups (median, 1,120 IU/ml in naïve nursing home residents and 2,211 IU/ml in controls). A large percentage of nursing home residents had SARS-CoV-2 S-reactive IFN-γ CD8(+) (naïve, 31/49; 63.2%; recovered, 8/10; 80%) or CD4(+) T cells (naïve, 35/49; 71.4%; recovered, 7/10; 70%) at baseline, in contrast to healthy controls (3/17, 17.6% and 5/17; 29%, respectively). SARS-CoV-2 IFN-γ CD8(+) and CD4(+) T-cell responses were documented in 88% (15/17) and all control subjects after vaccination, respectively, but only in 65.5% (38/58) and 22.4% (13/58) of nursing home residents. Overall, the median frequency of SARS-CoV-2 IFN-γ CD8(+) and CD4(+) T cells in nursing home residents decreased in post-vaccination specimens, whereas it increased in controls. CONCLUSION: The Comirnaty® COVID-19 vaccine elicits robust SARS-CoV-2-S antibody responses in nursing home residents. Nevertheless, the rate and frequency of detectable SARS-CoV-2 IFN-γ T-cell responses after vaccination was lower in nursing home residents compared to controls.