On Sept. 3, 2021, Moderna announced that it had submitted for a conditional marketing approval (CMA) with the European Medicines Agency (EMA) for the evaluation of a booster dose of the Moderna COVID-19 vaccine (mRNA-1273) at the 50 ﾵg dose level.

Neutralizing antibody titers had waned significantly prior to boosting at approximately 6 months. A booster dose of mRNA-1273 at the 50 ﾵg dose level boosted neutralizing titers significantly above the Phase 3 benchmark.