Paxton Bowers, 5, received a vaccine against Covid at Texas Children’s Hospital in November. Credit … Meridith Kohut for The New York Times
Scientific advisers at the Centers for Disease Control and Prevention voted unanimously Saturday to recommend vaccines against Covid for children under 5, the last group of Americans to qualify for vaccines, except babies under 6 months.
The director of the agency, Dr. Rochelle P. Walensky, is expected to approve the decision quickly. Parents should be able to start vaccinating their children as early as Tuesday.
Advisers were almost guaranteed to vote yes, despite reservations about the scarcity of data, especially with regard to the effectiveness of the Pfizer-BioNTech vaccine. Earlier this week, another group of experts advising the Food and Drug Administration unanimously supported vaccines.
Federal regulators have authorized the Modern vaccine for children 6 months to 5 years of age and the Pfizer-BioNTech vaccine for children 6 months to 4 years of age. (The Pfizer-BioNTech vaccine is available for children ages 5 and up from November.)
During a two-day meeting, CDC advisers heard evidence supporting the effectiveness of vaccines in younger children. But the committee repeatedly put pressure on Pfizer on its estimates and noted that three doses of this vaccine would be needed to protect children, compared to two doses of the Modern vaccine.
Both vaccines are safe and both produced antibody levels similar to those seen in young adults. But on Saturday, the CDC panel struggled with the difficulty of recommending two very different vaccines for the same population.
“Implementing these two releases will be incredibly difficult,” said Katelyn Jetelina, a public health expert and author of the widely read “Your Local Epidemiologist” newsletter.
“There will have to be a lot of proactive communication about the difference between the two and the implications of getting on top of each other,” he said.
In her clinical trials, Moderna found that two injections of her vaccine, each with a quarter of the adult dose, produced antibody levels at least as high as those seen in young adults.
The company estimated the effectiveness of the symptomatic infection vaccine at 51% among children 6 to 24 months of age and 37% among children 2 to 5 years of age. Side effects were minor, although about one in five children experienced a fever. The effectiveness against serious illness and death is thought to be higher, similar to the effects seen in adults.
Based on these data, the FDA authorized two injections of the Modern vaccine, four weeks apart.
The Pfizer-BioNTech vaccine also produced a strong immune response, but only after three doses, company officials told scientific advisers on Friday.
Two doses of the vaccine were inadequate, they said, justifying the FDA’s decision in February to delay the authorization of the vaccine until regulators had data on three doses. Two doses may not have been enough because the company gave children only a tenth of the adult dose on each injection, some counselors said.
The vaccine has an overall effectiveness of 80% in children under 5, Pfizer scientists said on Friday. But that estimate was based on only three children in the vaccine group and seven who received a placebo, making it an unreliable metric, CDC advisers said.
“We should assume we don’t have efficacy data,” said Dr. Sarah Long, an infectious disease expert at Drexel University School of Medicine. But Dr. Long said he was “comfortable enough” with other data supporting the vaccine’s potency.
Three doses of the Pfizer vaccine produced antibody levels comparable to those seen in young adults, suggesting that it is likely to be just as effective.
“The Pfizer is a three-dose series, but as a three-dose series, it’s quite effective,” said Dr. William Towner, who led vaccine trials for both Moderna and Pfizer at Kaiser Permanente south of California.
Any vaccine would be better than none, Dr. Towner added. He predicted that some parents may opt for Moderna because taking their children to a pediatrician for two injections is easier than getting them three.
The Pfizer vaccine was approved for children ages 5 to 11 in November, but less than 30 percent of that age group have received two injections. In the CDC polls, about half of parents said in February that they would vaccinate their children, but in May, only a third of parents said they wanted to.
Counselors discussed whether vaccination improves protection against serious illness in children who have already been infected. Little information is available for children between the ages of 5 and 11, due to the low absorption of vaccines in this age group.
But in adults, an infection with the previous variant of Omicron has not been enough on its own to protect itself from newer versions.
Vaccines would still be needed to protect children from future variants, experts concluded. “This combined protection is really the safest and most effective,” said Dr. Sara Oliver, a CDC scientist who led the discussion Saturday.
Parents of younger children may be more willing to opt for a vaccine against Covid if it can be offered along with other routine immunizations, Dr. Towner said.
“This is an area that many people are not sure about right now,” he said. “I hope some guidance is offered on this.”