A smaller dose of Pfizer-BioNTech’s Covid-19 vaccine cleared its first regulatory hurdle Tuesday for use in young children, after a Food and Drug Administration advisory committee voted to recommend it for emergency use authorization for those ages 5 to 11.
The 17-0 vote, with one abstention, will now go to the FDA, which is expected to make a final ruling in the coming days. If authorized, the move would make nearly the entire U.S. population eligible for a Covid shot. Only children ages 4 and younger would remain ineligible.
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Despite the vote in favor, deciding whether the benefits of vaccination for young kids outweigh potential risks appeared to weigh heavily on the advisors.
“This is a much tougher one, I think, than we had expected coming into it,” said committee member Dr. Eric Rubin, editor-in-chief of the New England Journal of Medicine. “The data show that the vaccine works and it’s pretty safe, … [yet] we’re worried about a side effect that we can’t measure yet,” he said, referring to a heart condition called myocarditis.
Committee member Dr. Cody Meissner, a professor of pediatrics at Tufts University School of Medicine in Boston, agreed.
“I think the likelihood that this vaccine is going to be effective is pretty likely in the six to 11 year old age group,” Meissner said. “The issue is side effects or adverse events that might be occurring after the vaccines.”
Also at issue was whether the vaccinations were needed at all, given the generally lower risk to children.
“It just seems to me that in some ways, we’re vaccinating children to protect the adults, and it should be the other way around,” said committee member Dr. James Hildreth, president and CEO of Meharry Medical College in Tennessee. “I do believe that children at highest risk do need to be vaccinated. But vaccinating all of the children … that seems a bit that much for me.”
To committee member Dr. Amanda Cohn, a chief medical officer at the Centers for Disease Control and Prevention, the benefits of vaccination were much clearer.
“When I look at this question, it is pretty clear to me that the benefits do outweigh the risk, when I hear about children who are being put in the ICU, who are having long term outcomes after their Covid, and children are dying,” Cohn said. “We vaccinate routinely against a couple of vaccine-preventable diseases for which far fewer deaths and hospitalizations and ICU admissions occur.”
Dr. Paul Offit, a vaccine researcher at Children’s Hospital of Philadelphia and a committee member, acknowledged the difficulty of the decision.
“It’s always nerve racking, I think, when you’re asked to make a decision for millions of children based on studies of only a few thousand children,” he said. “The question is, when do you know enough? And I think we certainly know that there are many children between five and 11 years of age who are susceptible to this disease who could very well be sick and are hospitalized or die from it.”
The vaccine for children ages 5 to 11 is a smaller dose than the one given to those 12 and older — 10 micrograms of mRNA versus 30 micrograms. Like in adults, the full vaccination series consists of two doses given three weeks apart. The children’s doses will come in vials with an orange cap and an orange label. The doses for adults and teens come in vials with a purple cap and a purple label.
Though children are less susceptible to severe illness from Covid, more than 1.9 million children ages 5 to 11 have tested positive for the coronavirus over the course of the pandemic, and more than 8,400 have been hospitalized, said Dr. Fiona Havers, a medical officer with the CDC. When children are hospitalized with Covid, they’re more likely to be admitted to the intensive care unit and more likely to need a ventilator, compared with children hospitalized with the flu, she added.
Ninety-four children have died of Covid, making it the eighth leading cause of death in this age group, she said.
Children who test positive for Covid are also at risk for a rare inflammatory condition called MIS-C, or multisystem inflammatory syndrome in children. As of Oct. 4, as many as 5,217 children of all ages have developed MIS-C, and 46 have died, she said, adding that the condition was most common in children ages 5 to 11.
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Though most cases of the virus in children are mild, kids can still spread it to others, including family members and people at school, Havers said. Kids are at least as likely to be infected with the virus as adults, but those infections are less likely to be reported, she said. In other words, positive cases in children are likely being missed.
It remains unclear what effect the vaccine would have on transmission, and Pfizer’s trial in kids wasn’t designed to study that, Dr. William Gruber, a scientist at Pfizer, said during the meeting. However, he pointed to “real world evidence” suggesting that vaccination affects transmission in adults, adding that “it’s reasonable to expect that there’ll be some reduction in transmission” for kids.
It’s also unclear whether young children will eventually need a booster dose. Committee member Dr. Michael Kurilla, an infectious disease expert with the National Institutes of Health, pointed out that Pfizer had limited follow-up data, and asked if there is any reason to think that antibody levels wouldn’t decrease in children similar to what’s been observed in adults.
“Is the expectation that these children are going to need a booster in six months?” he asked.
Gruber responded that the company would have more information at the six-month follow-up.
In its presentation to the FDA, Pfizer said its vaccine was nearly 91 percent effective at preventing symptomatic illness in kids. There were three cases of Covid in the vaccine group, compared with 16 cases in the placebo group. The cases occurred in July through September, when the highly transmissible delta variant was dominant, suggesting that the vaccine held up well against it, Gruber said. (He added that 14 of the 19 cases were able to be sequenced and determined to be delta.)
Side effects of the vaccination included sore arms, fever and muscle aches. However, the FDA said that Pfizer’s trial wasn’t large enough to detect extremely rare side effects, including myocarditis that’s been observed after the second dose, particularly in younger men and teenage boys. Just over 1,500 children ages 5 to 11 received the vaccine in the Pfizer trial (another 750 received a placebo) and there were no cases of myocarditis.
The lack of data on myocarditis was a source of concern among committee members. In a presentation to the committee, Dr. Mathew Oster of the CDC’s Covid-19 Response Team, said that for 12- to 17-year olds who received two doses of the Pfizer vaccine, the rate was as high as 56.7 cases per million doses in the three weeks following vaccination.
Both Covid and MIS-C are also known to increase the risk of myocarditis, he said.
Despite the lack of data on myocarditis, committee member Offit said there were several reassuring factors, including the fact that children will be given a lower dose, and that it appears the risk for the condition is lower is younger children.
FDA scientists affirmed Pfizer’s data, concluding that the benefits of vaccination outweigh the risks in most scenarios when Covid was widespread. It was only when Covid cases were very low in the community — as was the case in June — that it did not appear beneficial to vaccinate children.
Pfizer’s Covid vaccine is fully approved for teens and adults 16 and older, and may be given under emergency use authorization for children and teens 12 to 15. It’s the most widely used vaccine in the U.S., with more than 243 million doses given as of Monday, according to the CDC.
Next week, an advisory panel for the CDC will convene to make additional recommendations about who should receive the shots, for example, whether the vaccines should be limited to certain groups of children. Once CDC Director Dr. Rochelle Walensky signs off on those recommendations, young children can get start getting their shots.
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