Scientists at the Food and Drug Administration on Friday said Moderna’s coronavirus vaccine for infants and young children was safe and effective, setting the stage for a review by the agency’s outside advisers Wednesday and a potential authorization by the end of the week.
Moderna has asked the FDA for permission to use its vaccine in children 6 months through 5 years old. The Pfizer-BioNTech request is for children 6 months through 4 years old. The FDA is expected to release its assessment of the Pfizer-BioNTech vaccine in the next few days.
The FDA said the Moderna two-shot regimen for the youngest children met the main requirement set by regulators — that it generate an immune response at least as strong as the protection afforded young adults. The vaccine, according to data from the company and confirmed by the FDA, was only somewhat effective in preventing illness among the youngest group of recipients, reflecting the impact of the highly transmissible omicron variant, which has blunted the power of the vaccine in adults as well.
In examining side effects, the agency said adverse reactions in younger children were generally lower compared with those observed in adolescents and young adults, except for fevers. The FDA said the rates of fevers after vaccination were not “substantially different” than for other childhood vaccines.
In addition to the youngest children, Moderna is seeking authorization for its vaccine for children 6 to 17 years old. The agency gave a similarly favorable evaluation for those ages. The company’s request for the older children and teenagers will be reviewed Tuesday by the advisory committee.
Only Pfizer-BioNTech shots are authorized for Americans under 18.
The FDA said that, taken together, the Moderna data on safety, immune response and effectiveness indicates the pediatric vaccine has “a favorable benefit-risk profile in all age groups evaluated.”
While youngsters don’t usually become seriously ill with covid-19, more than 1,200 children and adolescents have died in the United States since the beginning of the pandemic in early 2020. And hospitalizations increased during the wave spawned by the omicron variant of the coronavirus.
If all goes as expected — the FDA is not required to follow the recommendations of its outside experts, but often does — the agency will authorize the Moderna and Pfizer-BioNTech vaccines for the youngest children soon after the advisory committee meeting. Assuming the Centers for Disease Control and Prevention and its advisers recommend the shots, the vaccines will be available in pediatricians’ offices, hospitals, clinics and certain pharmacies beginning the following week.
The Biden administration has been foreshadowing the regulatory action for days, pledging to speed supplies to an array of distribution sites. White House health officials said Thursday they are working closely with community and medical groups to ensure families have answers to questions about the vaccines.
Moderna’s two doses for the youngest group are each 25 micrograms, one-quarter of the adult dose, administered four weeks apart. The vaccine was shown to be 51 percent effective in preventing illness in children between 6 months and 2 years old, and 37 percent effective in children 2 to 5 years old. The FDA said it expects the vaccine will provide stronger protection against severe disease and hospitalizations.
The Pfizer-BioNTech vaccine is three shots, with the second dose given three weeks after the first. The third shot typically is administered two months later. Each dose is three micrograms, one-tenth of the adult dose. An early analysis suggested the vaccine was 80 percent effective against symptomatic illness.
The pediatric trials for both vaccines were not primarily designed to measure whether the shots prevented symptomatic illness. Instead, following a regulatory path often used to expand vaccine eligibility into younger age groups, scientists measured the levels of virus-blocking antibodies in children’s blood and compared those measurements to the levels that were protective in young adults.
For all the pediatric age groups, the FDA said there was uncertainty surrounding the duration of vaccine effectiveness, which has waned over time in adults. In addition, the agency said based on experience with adults “it is likely that a booster dose will be needed to increase robustness, breadth, and duration of protection against currently circulating and emerging SARS-CoV-2 variants.”
Moderna had requested permission to use its vaccine in adolescents more than a year ago, but that authorization was held up by concerns about the risk of rare cardiac side effects — inflammation of the heart muscle and surrounding tissue — called myocarditis and pericarditis. Both Moderna and Pfizer-BioNTech vaccines have been linked to the heart problems in young adult males. Most cases are mild and inflammation caused by covid-19 tends to be more severe.
In the new briefing documents, the FDA said there were no confirmed cases of myocarditis or pericarditis in the Moderna trials for infants, children and adolescents.
In a submission to the FDA, Moderna said it has begun testing booster shots in all pediatric age groups. The ones for children under 6 will be the original vaccine or the company’s new bivalent version that also targets both the original strain and the omicron variant.
Once available, vaccines for the youngest children are unlikely to be immediately embraced by most parents. Fewer than 20 percent of parents say they plan to get their infants and young children immunized immediately, according to a Kaiser Family Foundation survey.
“There will be two types of parents: ones that will really embrace the vaccines and others who are going to wait and see” how other children do, said John P. Moore, a professor of microbiology and immunology at Weill Cornell Medicine.
Moore said that many parents of young children have been influenced by vaccine misinformation partly because the risks to children from the coronavirus are relatively slim.
“It can be serious for children, but that’s very rare,” Moore said. “It’s very different for Granny and Granddad, who are in a much higher risk group. For them, it is a no-brainer.”