On May 25, 2021, Moderna announced that the Phase 2/3 study of its COVID-19 vaccine (mRNA-1273) in adolescents had met its primary immunogenicity endpoint, successfully bridging immune responses to the adult vaccination.

In the study, no cases of COVID-19 were observed in participants who had received two doses of the Moderna COVID-19 vaccine using the primary definition. This study, known as the TeenCOVE study, enrolled more than 3,700 participants ages 12 to less than 18 years in the U.S.