Moderna on Tuesday announced results from a clinical trial that found its Covid-19 vaccine is safe and effective in children ages 12 to 17, paving the way for the vaccine to become the second in the United States to be authorized for use in adolescents.

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Trial results

For the trial, researchers followed 3,732 people ages 12 to 17, two-thirds of whom received two doses of Moderna's vaccine while the remainder received a placebo.

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The trial's primary focus was on whether the vaccine prompted a similar immune system response in adolescents as in adults, and according to Moderna, it achieved that result. Further, the company said that no cases of symptomatic Covid-19 were found among those who received both doses of the vaccine, and the vaccine was 93% effective at preventing symptomatic Covid-19 among those who received only one dose.

"Those cases that did occur between the two doses were mild, which is also a good indicator of protection against the disease," Saskia Popescu, an infectious disease epidemiologist at George Mason University, said.

The side effects observed in the trial were mild, Moderna said, and most commonly included injection site pain, headache, fatigue, muscle pain, and chills—similar to the side effects reported in adults.

Moderna said the participants in the trial will be monitored for a year following their second shot to evaluate the long-term protection and safety of the vaccine.

"We are encouraged that mRNA-1273 was highly effective at preventing Covid-19 in adolescents," Stéphane Bancel, CEO of Moderna, said. "It is particularly exciting to see that the Moderna Covid-19 vaccine can prevent SARS-CoV-2 infection."

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"These look like promising results," Kristin Oliver, a pediatrician and vaccine expert at Mount Sinai Hospital, said. "The more vaccines we have to protect adolescents from Covid, the better."

Next steps

Bancel said that Moderna will "submit these results to the U.S. FDA and regulators globally in early June and request authori[z]ation."

Currently, Moderna's vaccine is only authorized for use in those ages 18 and older. If authorized, it will be the second vaccine in the United States to be authorized for use in adolescents. The vaccine developed by Pfizer and BioNTech is currently authorized for use in people ages 12 and older.

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases and chief medical advisor to the White House, said earlier this month that elementary age children likely won't receive Covid-19 vaccines until the end of the year (Anthes, New York Times, 5/25; Boseley, The Guardian, 5/25; Bonifield/Mascarenhas, CNN, 5/25; Weise/Weintraub, USA Today, 5/25; Miller/Edwards, NBC News, 5/25).