In a Phase 2/3 trial of 3,732 children ages 12 to 17 in the United States, blood tests showed that the vaccine produced an immune response that was equivalent to earlier findings in adults.
The trial wasn’t designed to look specifically at efficacy. However, initial observations found that none of the children who received the vaccine got sick with Covid-19 starting 14 days after their second dose. Four of the children who received the placebo tested positive for Covid-19, which Moderna says is “consistent with a vaccine efficacy of 100%.” The company notes that figure could change as more data is collected.
In the trial, a case was defined as someone who had at least two coronavirus symptoms or one symptom and a positive Covid-19 test.
The company also reviewed how well the vaccine worked after just one dose. The results suggest the vaccine was 93% effective after one dose at preventing mild cases of Covid-19, involving only one symptom of coronavirus disease instead of two or more symptoms.
Moderna announced the results Tuesday in a news release, and the results have not yet been peer reviewed or published.
The company said the vaccine was “generally well tolerated” and that no significant safety concerns were identified. Side effects included headache, fatigue, muscle pain and chills after administration of the second dose. Pain at the injection site was also sometimes observed.
Moderna says it plans to submit the results to the US Food and Drug Administration in early June along with a request for authorization to use the vaccine in adolescents. It also plans to submit the data to a peer-reviewed publication.
The Moderna vaccine is already authorized for use in people ages 18 and older. After Moderna asks the FDA for emergency use authorization of its vaccine for adolescents, the agency will review data submitted by the company, potentially consulting its advisers. If the data is solid, the FDA will give the vaccine the green light for this vaccine to be used in younger people.
The FDA has already expanded the emergency use authorization for Pfizer/BioNTech’s Covid-19 vaccine to include people ages 12 to 15 earlier this month. The vaccine had previously been authorized for people ages 16 and older.
Because these vaccines have been used safely in adults, vaccine experts said that was a relatively easy process. The Pfizer decision was made without a meeting of the FDA’s independent Vaccines and Related Biological Products Advisory Committee. The US Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices met a few days later to recommend use Pfizer’s vaccines in adolescents.
Both Pfizer and Moderna are currently testing their vaccines in younger children, ages 6 months to 11 years. Because those age groups may require varying doses, the process will likely take a little longer.
Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, recently said elementary age children likely won’t be vaccinated until the end of the year.