But having a second vaccine available might not translate into a big bump in vaccinations, at least in the 6-to-11-year-old age group, in which demand has been weak. Only 29 percent of children in that group have received the two-shot regimen of the Pfizer-BioNTech vaccine, according to the CDC.
To increase uptake “really is going to require lots of one-on-one single conversations and educating providers and parents about the benefits,” said Amanda Cohn, chief medical officer of the CDC’s National Center for Immunization and Respiratory Diseases and a member of the advisory committee.
Even with the unanimous support for the vaccine, some of the advisers expressed concerns that the data on the vaccine were limited and outdated because trials were conducted before the emergence of the omicron variant of the coronavirus. They said the vaccine would probably be beneficial in preventing serious illness but not as helpful in blocking mild infections.
“We crossed a line,” when the highly transmissible omicron and its subvariants arrived, which require a third dose for protection, said Paul A. Offit, professor of pediatrics at Children’s Hospital of Philadelphia. He said he supported authorization — as long as a third Moderna dose is on the way.
“We’re at a different part in this pandemic,” Offit said. “I think the benefits clearly outweigh the risks, but I say that with the comfort being provided that there will be a third dose.” Children who get a two-dose series should not be considered “fully vaccinated,” he said.
Moderna told the advisers it is testing a booster shot for the 6-through-17 age groups and would seek FDA authorization in coming months — perhaps by July.
The meeting Tuesday kicked off one of the busiest weeks in vaccine policy since the start of the pandemic. On Wednesday, the agency’s outside experts, the Vaccines and Related Biological Products Advisory Committee, are scheduled to discuss whether vaccines from Moderna and Pfizer-BioNTech should be used for the youngest children. For the Pfizer-BioNTech shot, which includes babies and children 6 months through 4 years old. And for Moderna, it’s children 6 months through 5 years old.
If the FDA and CDC give their blessings later this week, the vaccines will be available beginning next week, Biden administration officials have said. Babies and young children are the only group who do not have access to a vaccine.
Tuesday’s action, however, was focused on use of the Moderna vaccine for children 6 through 17. The advisers considered two groups: 6 through 11 years old and 12 through 17. Both votes in favor of the authorization were 22 to 0.
Last week, FDA scientists said the shot was safe and effective for all pediatric age groups. The staff report said the Moderna data on safety, immune response and effectiveness demonstrated “a favorable benefit-risk profile.”
Some parents have questioned whether vaccines are needed for children now, given the relatively low risk posed by covid-19 to the young.
But Katherine E. Fleming-Dutra, medical officer with the coronavirus vaccine policy unit at the CDC’s National Center for Immunization and Respiratory Diseases, said it is impossible to predict which children will develop severe disease.
“Certainly, children with underlying medical conditions are more at risk, but half of children 6 months to 4 years who were hospitalized with covid-19 don’t have underlying medical conditions,” she said.
Moderna said in a presentation that for every 1 million doses of vaccine distributed in the United States, 95 hospitalizations and 24 intensive care unit stays for children 6 through 11 years old would be avoided. For children 12 through 17, 200 hospitalizations and 52 ICU stays would be avoided, the company estimated.
In clinical trials, the Moderna vaccine was shown to generate an immune response — virus-blocking antibodies — at least as strong as the protection afforded vaccinated young adults, the agency’s main yardstick for efficacy. The vaccine did not produce concerning side effects, the FDA said.
Testing of the pediatric coronavirus vaccines is not designed primarily to measure directly 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.
But the agency said the trials also produced limited “supportive evidence” on the vaccine’s effectiveness and on the impact of variants of the coronavirus on the vaccine.
The studies showed that, based on how many children developed covid in the vaccine versus placebo groups, the efficacy was 93 percent for children 12 through 17, who were tested when the original strain and the alpha variant were dominant. The rate was 77 percent for children 6 through 11 when the delta variant was causing the most infections. Efficacy dropped to 51 percent and lower for children younger than 6 who were tested during the surge caused by omicron, which also blunts the vacancy’s potency in adults. Overall, the number of covid cases was low.
The Moderna shots are administered 28 days apart. Children 6 through 11 receive 50 micrograms in each shot, half the adult dose. Teenagers are given the adult dose. The third, or booster, dose for both groups will be 50 micrograms, the company said.
Moderna had requested permission to use its vaccine in adolescents more than a year ago, but authorization was held up because of concerns about the risk of rare cardiac side effects — inflammation of the heart muscle and surrounding tissue — called myocarditis and pericarditis. Both the 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 tends to be more severe.
There were no confirmed cases of myocarditis or pericarditis in the Moderna trials for infants, children and adolescents — but the trials might have been too small to pick it up. FDA officials said the risk-benefit balance was favorable, but that the safety and effectiveness of the vaccine would be closely monitored as it enters the market and is more widely used.
The advisers raised questions about how long the Moderna vaccine would provide immune protection against the coronavirus and whether it would be effective against the omicron subvariants circulating in the United States.
“At the start of the pandemic, it’s pretty clear that the bar was somewhat lower in terms of vaccine efficacy because we were trying to get vaccines out the door and get the population protected,” said Wayne Marasco, professor of medicine at Harvard Medical School and at Dana-Farber Cancer Institute. But Marasco said he hopes that companies will develop vaccines that have better durability and provide protection against infection that lasts longer than a few months.