Interim results from a phase 3 trial of the Moderna mRNA-1273 severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine indicated 94% efficacy in preventing coronavirus disease 2019 (Covid-19).1 The durability of protection is currently unknown. We describe mRNA1273-elicited binding and neutralizing antibodies in 33 healthy adult participants in an ongoing phase 1 trial,2-4 stratified according to age, at 180 days after the second dose of 100 μg (day 209).

DOI: 10.1056/NEJMc2103916

Time Course of SARS-CoV-2 Antibody Binding and Neutralization Responses after mRNA-1273 Vaccination.

All the participants received 100 μg of mRNA-1273 on days 1 and 29, indicated by arrows. The numbers of participants in each age group with data available at day 209 are as follows: 18 to 55 years, 15 participants; 56 to 70 years, 9 participants; and 71 years or older, 9 participants. The titers shown are the binding to spike receptor–binding domain protein (the end-point dilution titer) assessed on enzyme-linked immunosorbent assay (ELISA) on days 1, 15, 29, 36, 43, 57, 119, and 209 (Panel A); the 50% inhibitory dilution (ID50) titer on pseudovirus neutralization assay on days 1, 15, 29, 36, 43, 57, 119, and 209 (Panel B); and the ID50 titer on the live-virus focus-reduction neutralization mNeonGreen test (FRNT-mNG) on days 1, 29, 43, 119, and 209 (Panel C). Lines show geometric mean titers for each age group; 𝙸 bars indicate 95% confidence intervals. The dashed line indicates the limit of detection for each assay.

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