UPDATED: FDA's Peter Marks to Congress: Youngest kids vaccine won't need to hit 50% efficacy mark
The FDA’s top vaccine leader told a congressional committee on Friday afternoon that although the adult vaccines had to meet a 50% threshold for efficacy against Covid-19 infections, that same standard will not need to be met for the vaccines for the youngest group of children, for which a vaccine is not yet available.
The agency is currently reviewing data from Moderna’s two-shot vaccine for this youngest group as it awaits further data from Pfizer on its potential three-dose shot. Moderna has said its vaccine is 51% effective in children 6 months to 2 years of age and 37% effective in 2- to 5-year-olds. The agency also previously scheduled and then canceled an adcomm to review data on two doses of Pfizer’s vaccine for children under the age of 5.
According to a readout of the meeting from the House select subcommittee on the coronavirus crisis, Marks explained that the FDA would not withhold authorization — despite previous guidance — for a pediatric vaccine solely because it did not reach a 50% efficacy threshold at blocking symptomatic infections. All of the other adult and children’s vaccines currently authorized in the US have lost significant amounts of efficacy due to the Omicron variant, but they still remain effective at reducing the risk of severe disease, hospitalization and death.
“If these vaccines seem to be mirroring efficacy in adults and just seem to be less effective against Omicron like they are for adults, we will probably still authorize,” Marks said.
Meanwhile, Marks directly addressed concerns that the agency might slow-play the Moderna application and wait to review both applications together, saying that the VRBPAC meetings set for next month will be moved up if necessary.
“Obviously if we get through reviews faster, then we will send them to committees sooner,” Marks said, according to Rep. Jim Clyburn’s account of the meeting. Marks also told Clyburn and his staff that VRBPAC members have reserved earlier dates, enabling FDA to potentially “move dates up even by a week for any of these reviews.”
But he also explained that reviewing these vaccines for the youngest children involves more “complexity” than the review of adult vaccines, and the agency’s review process may require more time.
He also said that the emergence of new variants made the process of reviewing vaccines more complex, explaining it “was a little simpler for the original submissions in late 2020 when we didn’t have the variants and tons of immunogenicity data to go through.
“At the end of the day, we want people to have confidence in getting vaccinated,” he said, according to Clyburn. Marks also reiterated the importance of vaccinations to protect children against the coronavirus, stating: “We need to get more kids vaccinated, not just in the younger than 5 age range, but also older than 5.”
Since making these remarks to Clyburn, Marks told a media briefing earlier this week that he will maintain the standard for 50% efficacy for this shot for the youngest kids group, but that “it’s possible in subpopulations they might be a little less effective than 50%.”
Editor’s note: Article updated with Marks’ latest comment and to note Moderna’s stated efficacy for its vaccine for these two groups of the under 6 population.