A child is administered a dose of the Pfizer-BioNTech COVID-19 pediatric vaccine, in San Jose, Costa Rica, on Feb. 23.MAYELA LOPEZ/Reuters
A booster shot of the coronavirus vaccine made by Pfizer-BioNTech increased the level of neutralizing antibodies against both the original version of the virus and the omicron variant in a small trial of children age 5 to 11, the companies announced Thursday.
If the companies’ claims of a strong immune response pass muster with federal regulators, the government could broaden eligibility for booster doses to include 28 million more children.
The study by Pfizer and BioNTech, announced in December, included 140 children who received a booster six months after their second shot. The findings were described in a news release.
The children showed a sixfold increase in antibody levels against the original version of the virus one month after receiving the booster, compared with one month after receiving a second dose. Laboratory tests of blood samples from a subgroup of 30 children also showed 36 times the level of neutralizing antibodies against the omicron variant compared with levels after only two doses, according to the news release and a Pfizer spokeswoman.
The study did not show how long the antibodies last, or test effectiveness against COVID. The data was not published or peer-reviewed, and at least one expert said it was impossible to assess the study without more information.
Antibodies are the immune system’s first line of defense against infection. They are expected to rise after an additional dose; how rapidly that protection wanes has been an enduring concern for vaccine experts, regulators and manufacturers.
The companies said they would ask the Food and Drug Administration for emergency authorization of a booster for 5- to 11-year-olds “in the coming days.” The agency has typically acted within a month of receiving such requests.
Currently, Americans 12 and older are eligible for at least one booster, and about 30 million people age 50 or older are eligible for a second one. Studies suggest that 5- to 11-year-olds may particularly need a booster.
Researchers in New York state recently found that while two Pfizer shots protected children in that age group from serious illness, they provided virtually no protection against symptomatic infection, even just a month after full immunization.
“I think a bottom line is that in order to protect from the omicron, we know from studies and from adults and adolescents that you need three doses,” said Dr. Kathryn M. Edwards, a pediatric vaccine expert at Vanderbilt University School of Medicine. She predicted regulators would authorize the companies’ request.
But Dr. Philip Krause, who recently retired as a senior vaccine regulator at the FDA, questioned whether the sixfold increase in antibody levels in the overall group was the result of the additional shot or infection with the virus in the six month interim between the second and third dose.
“There are a lot of very important details that are missing,” he said of the companies’ statement.
Dr. Ofer Levy, a vaccine expert at Boston Children’s Hospital and a member of the FDA’s vaccine advisory board, said the results were helpful but the trial was modest in size, and no outcomes of safety or efficacy were cited.
“We presume that a higher level of antibodies is better and that’s probably true,” he said. “But how does that translate into vaccine effectiveness? We haven’t fully sorted that out.”
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