Comparative Immunogenicity and Effectiveness of mRNA-1273, BNT162b2, and Ad26.COV2.S COVID-19 Vaccines.

<bold>Background: </bold>Understanding immunogenicity and effectiveness of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines is critical to guide rational use.<bold>Methods: </bold>We compared the immunogenicity of mRNA-1273, BNT-162b2, and Ad26.COV2.S in healthy ambulatory adults. We performed an inverse-variance meta-analysis of population-level effectiveness from public health reports in > 40 million individuals.<bold>Results: </bold>A single dose of either mRNA vaccine yielded comparable antibody and neutralization titers to convalescent individuals. Ad26.COV2.S yielded lower antibody concentrations and frequently undetectable neutralization titers. Bulk and cytotoxic T-cell responses were higher in mRNA1273 and BNT162b2 than Ad26.COV2.S recipients. Regardless of vaccine, <50% of vaccinees demonstrated CD8+ T-cell responses. Antibody concentrations and neutralization titers increased comparably after the first dose of either vaccine, and further in recipients of a second dose. Prior infection was associated with high antibody concentrations and neutralization even after a single dose and regardless of vaccine. Neutralization of Beta, Gamma, and Delta strains were poorer regardless of vaccine. In meta-analysis, relative to mRNA1273 the effectiveness of BNT162b2 was lower against infection and hospitalization, and Ad26COV2.S was lower against infection, hospitalization, and death.<bold>Conclusions: </bold>Variation in the immunogenicity correlates with variable effectiveness of the 3 vaccines deployed in the United States. [ABSTRACT FROM AUTHOR]