Moderna Inc. said Thursday it expects people who received its two-dose Covid-19 vaccine to need a booster shot in the fall to keep strong protection against newer variants of the coronavirus.
The company said its vaccine remains 90% effective against preventing Covid-19 disease for at least six months, but said it sees a decline in antibody levels after six months, especially against newer strains of the coronavirus including the Delta variant. In a Phase 2 study, a third shot of the original formulation, as well as shots with vaccine candidates with adjusted designs, all showed robust antibody responses against Covid-19 variants of concern, Moderna said.