The EUA was originally issued on December 11, 2020, for administration in individuals 16 years of age and older. The FDA determined that the vaccine met the statutory criteria to amend the EUA, and that the known and potential benefits in individuals 12 years of age and older outweigh the known and potential risks.

The agency evaluated the safety of the vaccine in a population of 2,260 participants ages 12 to 15 years old that are enrolled in an ongoing randomized, placebo-controlled clinical trial in the U.S. Of these, 1,131 participants received the vaccine and 1,129 received a saline placebo. According to the sponsor, more than half of the participants were followed for safety for at least two months following the second dose.

The effectiveness of the vaccine was evaluated by comparing the immune response to the vaccine in 190 participants, 12 to 15 years of age, to the immune response of 170 participants, 16 to 25 years of age. The agency found that the response in younger adolescents was at least as good in the older group. Moreover, the vaccine was 100% effective in preventing COVID-19.