The Food and Drug Administration (FDA)’s Vaccines and Related Biological Products Advisory Committee voted unanimously (19 to 0) to amend the Emergency Use Authorization (EUA) for the Moderna COVID-19 vaccine (mRNA-1273) to allow for the use of a 50µg booster dose at least 6 months after completion of the primary series in:

  • Individuals 65 years of age and older,
  • Individuals 18 to 64 years old at high risk of severe COVID-19 disease, and
  • Individuals 18 to 64 years old with frequent institutional or occupational exposure to SARS-CoV-2 that puts them at increased risk for serious complications.

The need for a booster dose was prompted by real-world data suggesting waning protection, particularly against variants of concern, approximately 6 months after receipt of the primary series.

The panel reviewed safety and immunogenicity data from an ongoing phase 2 study in which immunocompetent adults received a 50µg booster dose of mRNA-1273 6 months after completing the 2-dose primary series with mRNA-1273 100µg.

Results showed that the booster dose increased neutralizing antibody titer responses against SARS-CoV-2 above the phase 3 benchmark. Similar levels of neutralizing titers were observed across age groups. As for safety, the adverse events profile following the booster dose was found to be similar to that seen after dose 2.

While not bound to the panel’s recommendations, the FDA will take them into consideration when making the final decision on authorization.

The Moderna COVID-19 vaccine is currently authorized for emergency use for active immunization to prevent COVID-19 disease in individuals 18 years of age and older. A third dose at the 100µg dose level has also been authorized for immunocompromised individuals 18 years of age and older.


  1. Vaccines and Related Biological Products Advisory Committee Meeting October 14, 2021. FDA Briefing Document. Accessed October 14, 2021.
  2. Moderna announces FDA advisory committee unanimously votes in support of emergency use for a booster dose of Moderna’s COVID-19 vaccine in the US. News release. October 14, 2021.