Humoral and adaptive immune responses to SARS-CoV-2 vaccine

Vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ameliorate infection and adverse outcomes from SARS-CoV-2. Elicitation of high affinity and durable protective antibody responses is a hallmark of a successful humoral immune response to vaccination. To assess the relevance of serum levels of SARS-CoV-2 specific antibodies and to further characterize the immune response to SARS-CoV-2 vaccines, we report: i) the levels of spike-binding and neutralizing antibodies to SARS-COV-2 in sera of thirty healthy volunteers at 9 months after the second vaccination dose of mRNA-vaccines and 1-month after the booster dose; ii) the levels of IFN-γ (Interferon-γ) production by blood T-cells exposed to SARS-CoV-2 spike antigen (Wuhan, Alpha B.1.1.7, Delta B.1.617.2, Omicron B1.1.529 variants); and iii) the specific phenotype of T-cells related with exposure to SARS-CoV-2 spike antigen. We observed that the booster dose induced increased humoral and adaptive immune responses and leads to early activation of memory CD8+ T subset.