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RESEARCH PRODUCT

Evolution of SARS-CoV-2 immune responses in nursing home residents following full dose of the Comirnaty® COVID-19 vaccine

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ABSTRACTObjectivesThere is scarce information as to the durability of immune responses elicited by the Comirnaty® COVID-19 vaccine in nursing home residents. Here, we assessed SARS-CoV-2-Spike (S)-targeted antibody and functional T cell responses at around 6 months after complete vaccination.MethodsThe sample comprised 46 residents (34 females; age, 60-100 years), of whom 10 had COVID-19 prior to vaccination. Baseline (median of 17.5 days after vaccination) and follow-up (median, 195 days) plasma specimens were available for quantitation of SARS-CoV-2-S antibodies and enumeration of SARS-CoV-2-S-reactive IFN-γ CD4+ and CD8+ T cells by flow cytometry.ResultsIn total, 44/45 participants had detectable SARS-CoV-2-S antibodies at follow-up. Overall, antibody levels were found to decrease (median, 4.8 fold). Antibodies waning was more frequent (P<0.001) in SARS-CoV-2 naïve (29/35) than in recovered (1/10) residents. SARS-CoV-2-S IFN-γ CD8+ T cells were detected in 33/46 and 24/46 at baseline and follow-up, respectively. The figures for CD4+ T cell counterparts were 12/46 and 30/46. Detectable SARS-CoV-2 IFN-γ CD8+ and CD4+ T cell responses at follow-up were more common in recovered (8/10 and 7/10, respectively) than in naïve residents (9/36 and 25/36, respectively). For those with detectable responses at both time points, SARS-CoV-2-S IFN-γ CD8+ T cell frequencies decreased significantly (P=0.001) over time whereas the opposite (P=0.01) was observed in CD4+ T cells.ConclusionAlmost all residents displayed detectable SARS-CoV-2-S-reactive antibodies and T cell responses, respectively, by around 6 months after complete vaccination with Comirnaty® COVID-19 vaccine, albeit generally waning in magnitude over time.