Scientific advisers from the Centers for Disease Control and Prevention began meeting Saturday to decide whether the benefits of Covid vaccines outweigh the risks for children under 5, one of the last groups of Americans to qualify. for vaccines.
The meeting, which is broadcast live here, began at 10 a.m. ET. The advisers are expected to vote in favor, despite reservations about the paucity of data, especially on the efficacy of the Pfizer-BioNTech vaccine.
Earlier this week, another expert panel that advises the Food and Drug Administration unanimously backed the vaccines. The FDA on Friday authorized the Moderna vaccine for children 6 months to 5 years old and the Pfizer vaccine for children 6 months to 4 years old. (The Pfizer-BioNTech vaccine has been available for children ages 5 and older since November.)
On Friday, CDC advisers heard evidence supporting the effectiveness of vaccines in younger children. But the committee repeatedly pressed Pfizer on its estimates, noting that three doses of that vaccine would be needed to protect children, compared with two doses of the Moderna vaccine.
Both vaccines are safe and both produced antibody levels similar to those seen in young adults. If the committee’s endorsement on Saturday is quickly followed by a green light from agency director Dr. Rochelle Walensky, states are preparing to start immunizing children next week.
Among the tasks facing the CDC panel on Saturday is the difficulty of recommending two very different vaccines for the same population.
“Implementing these two releases is going to be incredibly challenging,” said Katelyn Jetelina, a public health expert and author of the widely read newsletter “Your Local Epidemiologist.”
“There is going to have to be a lot of proactive communication about the difference between the two and the implications of taking one over the other,” he said.
In its clinical trials, Moderna found that two injections of its vaccine, each containing a quarter of the adult dose, produced antibody levels that were at least as high as those seen in young adults.
The company estimated the vaccine’s efficacy against symptomatic infection to be about 51 percent among children 6 to 24 months old and 37 percent among children 2 to 5 years old. Side effects were minor, although about one in five children experienced a fever.
Based on that data, the FDA authorized two injections of the Moderna vaccine, spaced 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.
They said that two doses of the vaccine were inadequate, justifying the FDA’s decision in February to delay 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 in each injection, some advisers said.
The vaccine has an overall efficacy of 80 percent in children under 5 years old, Pfizer scientists said Friday. But that estimate was based on just three children in the vaccine group and seven who received a placebo, making it an unreliable metric, CDC advisers noted.
“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 she was “comfortable enough” with other data supporting the vaccine’s potency.
Three doses of Pfizer’s vaccine produced antibody levels comparable to those seen in young adults, suggesting that it is likely to be just as effective.
“Pfizer is a three-dose series, but as a three-dose series it’s pretty effective,” said Dr. William Towner, who led vaccine trials for both Moderna and Pfizer at Kaiser Permanente in Southern California.
Any vaccine would be better than none, added Dr. Towner. He predicted that some parents may opt for Moderna because taking children to the pediatrician for two injections is easier than arranging for three doses.
Pfizer’s vaccine was licensed for children ages 5 to 11 in November, but fewer than 30 percent in that age group have received two shots. Parents of younger children may be more willing to opt for a Covid vaccine if it can be offered along with other routine immunizations, Dr. Towner said.
“That’s the area that a lot of people aren’t sure about right now,” he said. “I hope some guidance will be offered on that.”