SARS-CoV-2 mRNA vaccine BNT162b2 triggers a consistent cross-variant humoral and cellular response

As the SARS-CoV-2 pandemic continues to rage world-wide, the emergence of numerous variants of concern (VOC) represents a challenge for the vaccinal protective efficacy and reliability of commercially available high-throughput immunoassays. Our study demonstrates that, the administration of two doses of BNT162b2 vaccine elicited a robust SARS-CoV-2-specific immune response assessed up to three months after full vaccination in a cohort of 37 health care workers (HCWs). SARS-CoV-2 specific antibody response, evaluated by four commercially available chemiluminescence immunoassays (CLIA), was qualitatively consistent with the results provided by the gold-standard in vitro neutralization assay (NTA). However, we could not observe a correlation between the quantity of antibody detected by CLIA assays and their neutralizing activity tested by NTA. Almost all subjects developed a SARS-CoV-2 specific T cell response. Moreover, vaccinated HCWs developed a similarly protective neutralizing antibodies response against the EU (B.1), Alpha (B.1.1.7), Gamma (P.1), and Eta (B.1.525) SARS-CoV-2 variants, while Beta (B.1.351) and Delta (B.1.617.2) strains displayed a consistent partial immune evasion. These results underline the importance of a solid vaccine-elicited immune response and a robust antibody titer. We believe that these relevant results should be taken into consideration in the definition of future vaccinal strategies.