On Oct. 20, 2021, Moderna announced that the U.S. Food and Drug Administration (FDA) had authorized for emergency use a booster dose of the Moderna COVID-19 vaccine (mRNA-1273) at the 50 ﾵg dose level for people aged 65 and older; people aged 18 to 64 who are at high risk of severe COVID-19; and people aged 18 to 64 with frequent institutional or occupational exposure to SARS-CoV-2.

The booster dose was to be administered at least six months after completion of the primary series. The FDA also authorized a single booster dose of the Moderna COVID-19 Vaccine for individuals who had completed a primary vaccination with other authorized or approved COVID-19 vaccines.

The FDA based this EUA on the totality of scientific evidence shared by the company and reviewed by the FDA’s Vaccines and Related Biological Products Advisory Committee (VRBPAC), including a data analysis from the Phase 2 clinical study of mRNA-1273, which was amended to offer a booster dose of mRNA-1273 at the 50 µg dose level to interested participants 6-8 months following their second dose (n=344). Neutralizing antibody titers had waned prior to boosting, particularly against variants of concern, at approximately 6 months.

Notably, a booster dose of mRNA-1273 at the 50 µg dose level boosted neutralizing titers significantly above the Phase 3 benchmark. After a booster dose, a similar level of neutralizing titers was achieved across age groups including in older adults (ages 65 and above).

The safety profile following the booster dose was similar to that observed previously for dose 2 of mRNA-1273. The positive vote was unanimous with 19 VRBPAC members recommending EUA.