Moderna’s Covid Vaccine is Effective in Children Under 6, F.D.A. Says

Moderna’s coronavirus vaccine for children under 6 is effective in preventing symptomatic infection without causing worrisome side effects, the Food and Drug Administration said on Friday night.

Advisers to the F.D.A. are scheduled to meet next week to decide whether to recommend that the agency grant Moderna’s request for emergency authorization of its vaccine for children ages 6 months to 17 years. They will also consider an application from Pfizer and its German partner, BioNTech, to clear its pediatric vaccine for children under 5. The F.D.A. is expected to release its analysis of Pfizer’s application on Monday.

The F.D.A. cautioned that estimates of the efficacy of Moderna’s two-dose pediatric vaccine were based on relatively few cases of Covid-19. The agency also said that, like adults, pediatric recipients would probably require a booster shot to counteract the vaccine’s waning potency over time.

But the agency said that two shots of Moderna’s vaccine triggered an immune response in clinical trial participants comparable to that of young adults, meeting the criterion set for effectiveness. The results were measured by the level of neutralizing antibodies, which work to block the virus, in the children’s blood.

Children 11 and younger generally experienced fewer side effects from the vaccine than adolescents, probably because their doses were weaker, the F.D.A. said. Although fevers were more frequent in children under 6, the rates were not substantially different from those produced by other routine childhood vaccines, the agency said.

There were no cases of myocarditis or pericarditis, conditions involving inflammation of the heart muscle and surrounding tissue that are known risks for young men who receive Moderna or Pfizer coronavirus vaccines.

The roughly 18 million children under 5 are the only group in the United States not eligible for Covid shots. Those 5 or over are covered by the Pfizer-BioNTech vaccine.

Moderna and Pfizer are proposing different regimens to cover the youngest children. Pfizer is seeking authorization for a three-dose regimen with doses one-tenth the strength of adult shots. Moderna has proposed two doses at one-quarter the strength of adult doses.

Moderna’s vaccine was 51 percent effective in preventing symptomatic infection in children 6 months to 2 years old and 37 percent effective in children 2 to 5 years old. Pfizer said its clinical trial suggested that its vaccine was 80 percent effective, but the trial was based on 10 cases. More than twice that number is required to assess the efficacy of the shots.

Anticipating regulatory authorization of one or both vaccines, the White House outlined this week its initial plan to make shots available for children under 5, starting the week of June 19. Biden administration officials said that the government had made 10 million doses available to states and health providers.