FDA advisers endorse administration of Moderna, Pfizer Covid-19 vaccines in babies, toddlers

The FDA’s independent vaccine advisers voted unanimously Wednesday to recommend the agency authorize two Covid-19 vaccines for babies, toddlers and preschool-age children, putting the country’s youngest age group one step closer to immunizations nearly two-and-a-half years into the pandemic.

The 21-member panel — comprised of pediatricians, infectious disease experts and vaccine researchers — found that the benefits of vaccinating children under 5 against Covid with either vaccine outweigh potential risks.

The FDA is expected to quickly authorize for emergency use the Pfizer-BioNTech vaccine for kids under 5 and the Moderna vaccines for kids under 6. Both options could be used in children as young as 6 months old.

The CDC’s panel of expert advisers will consider whether to recommend the shots’ administration during meetings on Friday and Saturday. Once CDC Director Rochelle Walensky signs off on a recommendation, children are expected to begin receiving shots by Tuesday. Children under 6 who receive the Moderna vaccine will get two 25-microgram doses, four weeks apart. The Pfizer vaccine is two 3-microgram doses three weeks apart, followed by a third dose at least eight weeks later.

Some panel members signaled concern that parents may get confused by the products' different dose regimens — particularly since the Pfizer-BioNTech vaccine doesn't offer much protection after two doses, while Moderna's primary series is complete with two doses.

"I have a lot of concern that many of these kids will not get the third dose," Jeannette Yen Lee, a biostatistics professor at the University of Arkansas for Medical Sciences, said of the Pfizer vaccine. "It's a struggle to get people in for two," she added, noting that booster uptake for older populations is also low.

Michael Nelson, chief of UVA Health's asthma, allergy and immunology division, urged the manufacturers to quickly gather data on the prospect of vaccinating these children against Covid at the same time they receive other routine immunizations.

“If we don’t get a quick answer to the coadministration question, it will serve as a barrier to completion of the three-dose series for [the Pfizer] vaccine and likely for the Moderna vaccine," he said. "Having to get it in isolation is going to be a great challenge to families and children here in the U.S."

Peter Marks, FDA’s top vaccine regulator, started the daylong meeting pointing to the burden of Covid hospitalizations for young children during the recent Omicron wave at rates that have equaled or exceeded those for other common childhood vaccine-preventable diseases like the flu. More than half of children under 5 who have been hospitalized for Covid did not have underlying health conditions, and 202 in the 6-month to 4-year-old age group have died of the disease as of May 11.

“The intervention we’re talking about here is one that is something that we have accepted in the past to try to prevent deaths from influenza,” he said. “Here we have a different pathogen, but one that has created a lot of havoc just the same.”

The Biden administration is girding for a slog in convincing parents to quickly vaccinate their young children. Summer vacations — and young children receiving various levels of schooling before age 5 — along with misinformation about vaccines could depress early turnout. Many young children also contracted Covid during the Omicron surge, which could convince parents to hold off on immunizing them until they’re further removed from their natural infections.

Recent polling by the Kaiser Family Foundation suggests about 20 percent of parents are eager to vaccinate their children under 5 as soon as they’re allowed, while nearly 40 percent plan to “wait and see” how the vaccine works and another 40 percent are reluctant to immunize at all.

Just 29 percent of U.S. children ages 5 to 11 are fully vaccinated against Covid, compared to nearly 56 percent of 12- to 15-year-olds and 67 percent of 16- and 17-year-olds, according to CDC data ending April 30.

The FDA analyzed the vaccines' ability to induce neutralizing antibody responses in kids that were comparable to young adults, a concept known as immunobridging. Both met the agency's success criteria.

Real-world efficacy against the Omicron variant in the 6-month-to-5-year-old age group for Moderna's vaccine ranged from 36 percent to 51 percent, and efficacy estimates were "generally consistent" with rates seen in observational studies of adults during the same variant waves, the FDA said.

Preliminary analyses of the Pfizer vaccine showed efficacy of 80 percent in kids under 5 against disease, though only 10 Covid cases were reported among study participants before the data cutoff date in April, limiting confidence in that figure.

Panel member Amanda Cohn of the CDC expressed concern that parents will compare efficacy percentages put forward by the companies and base which product they pick solely on those numbers.

“My level of confidence in that number ... I do not have any idea what that number will end up being," she said of the 80 percent figure for Pfizer's vaccine, adding that she does think it is effective.

In both companies' data, there were several unknowns that reflect the current state of adult vaccination in the U.S., including duration of effectiveness and how well vaccination protects against outcomes like long Covid, the FDA said. Children will likely need booster doses in the future, given adults' experience with waning antibody protection, reviewers said.

Adverse reactions like headaches and fatigue were more common in teens than in younger kids, likely because they received larger vaccine doses, the FDA said. Fever was reported more frequently among the youngest vaccine recipients.

The manufacturers did not report any events in their trials that met the CDC definition for probable or confirmed myocarditis or pericarditis — two types of heart inflammation that have been detected as potential side effects of the messenger RNA vaccines, particularly for males ages 12 to 39.

The FDA's reviews of Pfizer’s and Moderna’s data come after months of angst from parents who felt strung along by statements that Covid-19 vaccines would be available for the country's youngest children by early 2022, only to see dates shift. The FDA scheduled an advisory committee meeting in February to consider a two-dose primary series of Pfizer's vaccine, only to pull back once the data suggested a third dose could bolster its effectiveness.

Parents and advocates for children under 5 to get access to vaccines erupted over a POLITICO report in April that the Biden administration was leaning toward authorizing both Pfizer-BioNTech's and Moderna's products at the same time to make it easier to promote the shots, a move some believed resulted in regulators sitting on Moderna's application while Pfizer continued to collect data and complete its submission. FDA Commissioner Robert Califf later insisted there would be no holdup on Moderna's application, but the advisory committee meeting schedule ultimately ensured both vaccines would be considered head-to-head.

Parents who spoke during the public comment period Tuesday and Wednesday indicated they were still angry at the perceived delay, noting that most children who end up receiving Pfizer’s three-dose series won’t be fully vaccinated by the time the school year starts.

“We have waited too long, and too many families have suffered already,” said Fatima Khan, cofounder of Protect Their Future, a grassroots group that has advocated for vaccine access for the youngest kids.

Arnold Monto, the committee's acting chair and a University of Michigan infectious disease expert, said the 18-month gap in making Covid vaccines available to the youngest children in the U.S. was a function of needing to take extra care with trialing the immunizations, along with determining how best to vaccinate older Americans as the pandemic evolved.

"To say there have been delays, unnecessary delays, is not representing the true situation, which involved not working with adults but with a vulnerable, younger population for whom special care is necessary," he said.