BACKGROUND: mRNA-1273 vaccine demonstrated 93.2% efficacy against Coronavirus disease 2019 (COVID-19) in the Coronavirus efficacy (COVE) trial. The humoral immunogenicity results are now reported. METHODS: Participants received two mRNA-1273 (100 µg) or placebo injections, 28 days apart. Immune responses were evaluated in a pre-specified, randomly-selected per-protocol immunogenicity population (n = 272 placebo; n = 1,185 mRNA-1273). Serum binding (bAb) and neutralizing (nAb) antibodies to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)-spike protein were assessed at days 1, 29, and 57 by baseline SARS-CoV-2-negative (n = 1,197) and -positive (n = 260) status, age and sex. RESULTS: SARS-CoV-2-negative vaccinees had bAb geometric mean (GM) AU/ml levels of 35,753 at day 29 that increased to 316,448 at day 57 and nAb ID50 titers of 55 at day 29 that rose to 1081 at day 57. In SARS-CoV-2-positive vacinees, the first mRNA-1273 injection elicited bAb and nAb levels that were 11-fold (410,049) and 27-fold (1,479) higher than in SARS-CoV-2-negative vaccinees, respectively, and were comparable to levels after two injections in uninfected participants. Findings were generally consistent by age and sex. CONCLUSION: mRNA-1273 elicited robust serologic immune responses across age, sex, and SARS-CoV-2-status, consistent with its high COVID-19 efficacy. Higher immune responses in those previously-infected support a booster-type effect.ClinicalTrials.gov: NCT04470427.
Humoral Immunogenicity of the mRNA-1273 Vaccine in the Phase 3 COVE Trial