Scientific advisers from the Centers for Disease Control and Prevention are meeting on Saturday to decide whether the benefits of Covid vaccines outweigh the risks for children under 5, the last Americans to qualify for vaccines.
The meeting, which will be streamed live here, is scheduled to begin at 10 a.m. Eastern Time. Advisors are almost certain to vote yes, despite reservations about the lack of data, especially regarding the effectiveness of the Pfizer-BioNTech vaccine.
Earlier this week, another group of experts advising the Food and Drug Administration unanimously backed the vaccines. The FDA on Friday authorized the Moderna vaccine for children ages 6 months to 5 years and the Pfizer vaccine for children ages 6 months to 4 years. (Pfizer-BioNTech’s 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 and noted that three doses of this vaccine would be needed to protect children, compared to 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 approval on Saturday is quickly followed by a green light from the agency’s director, Dr. Rochelle Walensky, states are preparing to start vaccinating 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 deployments is going to be incredibly difficult,” said Katelyn Jetelina, public health expert and author of the widely read “Your Local Epidemiologist” newsletter.
“It’s going to take a lot of proactive communication about the difference between the two and the implications of taking one over the other,” she said.
In its clinical trials, Moderna found that two shots of its 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 vaccine’s effectiveness against symptomatic infections at around 51% in children aged 6 to 24 months and 37% in children aged 2 to 5 years. Side effects were minor, although around one in five children had a fever.
Based on this 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.
Two doses of the vaccine were insufficient, they said, justifying the FDA’s decision in February to delay licensing the vaccine until regulators had data on three doses. Two doses may not have been enough, as the company only gave children a tenth of the adult dose with each injection, some advisers said.
The vaccine has an overall effectiveness of 80% in children under 5, Pfizer scientists said on Friday. But that calculation was based on just three children in the vaccinated group and seven who received a placebo, making it an unreliable measure, CDC advisers noted.
“We should just assume that we don’t have efficacy data,” said Dr. Sarah Long, an infectious disease expert at Drexel University College of Medicine. But Dr Long said she was “quite comfortable” with other data supporting the potency of the vaccine.
Three doses of the Pfizer vaccine produced antibody levels comparable to those seen in young adults, suggesting 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 Moderna and Pfizer at Kaiser Permanente in California from South.
Either vaccine would be better than none, Dr Towner added. He predicted that some parents might opt for Moderna because it’s easier to get kids to a pediatrician for two shots than to have them get three doses.
The Pfizer vaccine was licensed for children ages 5 to 11 in November, but less than 30% of 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 alongside other routine vaccinations, Dr Towner said.
“That’s the area that a lot of people are unsure about right now,” he said. “Hopefully there will be guidance on this.”