RESUMO
IntroductionThe waning of the antibody titre after the first two doses of the Pfizer-BioNTech BNT162b2 mRNA SARS-CoV-2 vaccine was reported. However, knowledge of the dynamics of cellular immunity is scarce. Here, we performed a prospective cohort study to disclose antibody and cellular immunity dynamics and discuss the relationship between immunity and breakthrough infection. MethodsThe study had a prospective cohort design. Antibody titres against SARS-CoV-2 in serially collected serum samples of 608 Japanese vaccinees after 6 months of vaccination were measured. Simultaneously, T-cell immunity dynamics were assessed using the QuantiFERON SARS-CoV-2 assay. Additionally, participants with suspected breakthrough infection were detected according to the positive conversion of the IgG assay for nucleocapsid proteins of SARS-CoV-2. ResultsAntibody titres were elevated 3 weeks after vaccination and waned over the remainder of the study period. The QuantiFERON SARS-CoV-2 assay performed on 536 participants demonstrated the similar dynamics. Six participants without predisposing medical conditions demonstrated positive conversion of the IgG assay for nucleocapsid proteins, while five were asymptomatic. ConclusionWaning of humoral and cellular immunity within 6 months of administration of two doses of BNT162b2 vaccine among Japanese healthcare professionals and the occurrence of asymptomatic breakthrough infection was suspected in approximately 1 of 100 vaccinees. (UMIN000043340)
RESUMO
Generation of antigen-specific memory T cells has been analyzed only for few coronavirus disease 2019 (COVID-19) vaccinees, whereas antibody titers have been serologically measured for a large number of individuals. Here, we assessed the anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) cellular immune response in a large cohort using interferon (IFN)-{gamma} release assays (IGRAs) based on short-term whole blood culture. The study included 571 individuals who received the viral spike (S) protein-expressing BNT162b2 mRNA SARS-CoV-2 vaccine. Serum IgG titers against the receptor-binding domain (RBD) of S protein were measured. Samples of 28 vaccinees were subjected to flow cytometry analysis of T cells derived from short-term whole blood culture. IFN-{gamma} production triggered by S antigens was observed in most individuals 8 weeks after receiving the second dose of the vaccine, indicating acquisition of T cell memory responses. The frequencies of activated T cell subsets were strongly correlated with IFN-{gamma} levels, supporting the usability of our approach. S antigen-stimulated IFN-{gamma} levels were weakly correlated with anti-RBD IgG titers and associated with pre-vaccination infection and adverse reactions after the second dose. Our approach revealed cellular immunity acquired after COVID-19 vaccination, providing insights regarding the effects and adverse reactions of vaccination.
