FDA on Friday announced it would delay its review of Pfizer-BioNTech's Covid-19 vaccine for children under 5 as it awaits data from the companies' ongoing vaccine trial.

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Background

Earlier this month, FDA asked Pfizer and BioNTech to submit an application for emergency use authorization (EUA) for two doses of its Covid-19 vaccine in children under the age of 5—although clinical trial data suggests that a third dose may be necessary for adequate protection.

In December, the companies announced that children between the ages of 6 months and 2 years who were given two doses of the Covid-19 vaccine at a tenth of the adult dosage saw a robust immune response, but the same response did not occur among children ages 2 to 4. As a result, Pfizer and BioNTech are currently evaluating how effective a third dose of the vaccine will be for this age group, with results expected in late March.

One person familiar with the situation said the EUA application was aimed at getting children two shots for now, with a third dose possible later.

"We know that two doses [aren't] enough, and we get that," the person said. "The idea is, let's go ahead and start the review of two doses. If the data holds up in the submission, you could start kids on their primary baseline months earlier than if you don't do anything until the third-dose data comes in."

FDA delays review of vaccine

The Vaccines and Related Biological Products Advisory Committee was scheduled to review Pfizer-BioNTech's application on Tuesday, however according to a statement from FDA, Pfizer recently disclosed "additional findings from its ongoing clinical trial" which led FDA to postpone the meeting.

According to Peter Marks, director of FDA's Center for Biologics Evaluation and Research, "the data that we saw made us realize that we needed to see data from a third dose in the ongoing trial in order to make the determination that we could proceed with doing an authorization. I think parents can feel reassured that we have set a standard by which we feel that if something does not meet that standard, we can't proceed forward."

Marks added that FDA has a responsibility to act quickly given the size and impact of the omicron surge on children.

"We had days when we were getting above three-quarters of a million cases a day of omicron, and we started to see a tremendous number of children affected by omicron," he said.

In a statement, Pfizer said a third dose of its vaccine "may provide a higher level of protection in this age group" based on the results from studies on booster doses that found three doses improved antibody levels and "real-world protection."

Mixed reaction from parents and experts

Many parents expressed frustration with FDA's decision. "Ever since the vaccine came out, we've been looking forward to a time when our son would be vaccinated and could start to have a normal childhood," said Andrew, a parent of a young child who spoke to the Washington Post.

"It's really just pushing the risk assessment onto the parents," he added. "In the very unlikely event that something happens with the vaccine that's on [FDA]. But if your kid gets sick and gets a very rare but serious complication, that's on you, the parents."

Joel Wertheimer, a father of a 4-month-old, who spoke to the Post, said that even if two doses of the vaccine provide a small amount of protection, he'd want to get his child vaccinated as soon as possible

"We do this all the time, we do things that increase our children's safety by 20% or 30% … like certain car seats and certain cribs," he said.

"I was hoping that we would have some hope, that it would help us get some semblance of normalcy," Rachel Perera, a parent of an 8-month-old, told the New York Times. "I feel like the world is moving on without us, the parents of little kids."

Natasha Burgert, a pediatrician in Kansas, said she's "gutted" by the decision. "We need this protection for our kids," she said.

Burgert added that some families are relieved by the decision "because they didn't want to make that decision without good efficacy data. Other groups of parents are just crying out, 'Give us a choice. Show us what you've got and let us make a choice. Let us have access to it.'"

However, some health experts praised FDA for its decision.

"As much as I want a vaccine for these younger children, I also do think it is important to follow the process and follow the data," said Sean O'Leary, vice chair of the American Academy of Pediatrics Committee on Infectious Diseases, adding that FDA's decision was a judgment call that "makes a lot of sense."

"The plan to have two doses be given while waiting data on a third dose never made sense to me," said Leana Wen, an emergency physician and public health professor at George Washington University. "You can't just approve something and say it's safe and effective if you haven't seen the data."

"At the end of the day, the FDA asked for the data, Pfizer was willing to give it to them—and in the 11th hour, the decision was made: We're not yet ready to provide that information, because it's going to be more confusing," said C. Buddy Creech, director of the Vanderbilt Vaccine Research Program. "I'm a big fan of trusting the process." (Walker, MedPage Today, 2/11; McGinley et al., Washington Post, 2/11; LaFraniere/Weiland, New York Times, 2/11; Herper et al., STAT News, 2/11; Reed, Axios, 2/12; Neergaard/Perrone, Associated Press, 2/11)