Phase I vaccine results
A messenger RNA (mRNA) vaccine has shown promise against SARS-CoV-2 in humans in a phase I study. All 45 participants in the trial seroconverted by day 15 after the first dose. Two weeks after the second dose of the 25-µg vaccine, levels of binding antibodies were similar to those observed in convalescent sera from recovered patients. The first eight participants given the vaccine all developed neutralizing antibodies (data were available for only these 8). Adverse events were rare. In a separate study, the vaccine blocked viral replication in the lungs of mice infected with SARS-CoV-2. Phase II of the study in humans is expected to begin shortly, and phase III could begin in July.