Reactogenicity, safety and antibody response, after one and two doses of mRNA-1273 in seronegative and seropositive healthcare workers.

• A single dose of mRNA-1273 appears to be sufficient in the vast majority of seropositive individuals prior to vaccination. • Previously infected workers experienced more frequent and severe common side effects after the first dose. • The second dose induced greater overall reaction than the first one regardless of the serological status. [ABSTRACT FROM AUTHOR]