Neutralization activity of sera/IgG preparations from fully BNT162b2 vaccinated individuals against SARS-CoV-2 Alpha, Beta, Gamma, Delta, and Kappa variants

In the present prospective study, 225 individuals in Kumamoto General Hospital, Japan, who received two-doses of BNT162b2 vaccine were enrolled/followed up over 150 days and neutralizing activity (NT(50)) of their sera and antiviral activity (EC(50)) of IgG purified from sera on day-60 post-1st-dose were determined against wild-type SARS-CoV-2 (SARS-CoV-2(Wuhan)) (n = 211) and 9 variants (Alpha, Beta, Gamma, Delta, and Kappa) (n = 45). Time-dependent changes of IgG-activity (n = 25) against SARS-CoV-2(Wuhan) and variants were also examined. Day-60 sera showed reduced NT(50) by more than 50% against all variants examined, and greatest reduction was seen with Beta. IgG fractions of high-responders and moderate-responders showed similar fold-changes in EC(50) against each variant compared to SARS-CoV-2(Wuhan). Evaluation of EC(50) of IgG obtained at different time-points (day-28 to -150) revealed time-dependent reduction of activity against all variants. However, against Delta, relatively long-lasting favorable antiviral activity (at least 150 days) was observed. Our data strongly suggest that the successful antecedent scale-up of mRNA-based vaccine administrations in Japan was the primary contributor to the lessening of the otherwise more devastating SARS-CoV-2 pandemic wave caused by the Delta variant. The present data that the effectiveness of vaccine against the then-dominant SARS-CoV-2 variant was likely associated with the moderation of the COVID-19 pandemic wave suggest that as in the case of influenza vaccines, the development of multivalent mRNA-based vaccines represent a generalizable approach to pre-emptively respond pandemic with mutable pathogens.