Pfizer-BioNTech Vaccine Is Highly Effective at Preventing Covid-19 Infections in Adolescents

In a study of 2,260 children age 12 to 15, no vaccinated kids contracted the virus

A young girl looks on as both of her grandparents are vaccinated at a clinic in Los Angeles
The new study compared 1,131 children between 12 and 15 years old who received two doses of the Pfizer-BioNTech vaccine, and 1,129 who received two doses of a placebo. Francine Orr / Los Angeles Times via Getty Images

The Covid-19 vaccine created by Pfizer and BioNTech strongly protects adolescents between the ages of 12 and 15 from developing symptomatic illness, according to the results shared in a statement on Wednesday. The data have not yet been peer-reviewed.

The vaccine is currently authorized for emergency use in people ages 16 and older in the United States. The trial in adolescents began in October and included about 2,300 participants, half of whom received the vaccine and half that got a saltwater placebo, Joe Palca reports for NPR. Over the course of the study, 18 kids who were not vaccinated tested positive for Covid-19, while nobody who received the vaccine developed symptoms of the disease.

“We plan to submit these data to FDA as a proposed amendment to our emergency use authorization in the coming weeks and to other regulators around the world, with the hope of starting to vaccinate this age group before the start of the next school year,” says Albert Bourla, Chairman and CEO of Pfizer, in the statement.

Pfizer-BioNTech’s vaccine was the first to receive emergency use authorization from the FDA on December 11 last year. The vaccine contains a small genetic messenger called mRNA carried inside of an oily shell. When someone gets the vaccine, their body reads that genetic message and creates a small piece of the coronavirus called the spike protein, which can’t cause an infection on its own. But a vaccinated person’s immune system can study the spike protein and learn how to fight the virus if they become exposed to it later.

While the immune system learns how to target the spike protein, people experience side effects like soreness and fever. Once the immune system has studied up, it creates a flood of antibodies that are trained to target and destroy the spike protein, and the whole virus along with it.

The new study compared 1,131 children between 12 and 15 years old who received two doses of the Pfizer-BioNTech vaccine, and 1,129 who received two doses of a placebo. Those who were vaccinated showed similar side effects to vaccinated people between the ages of 16 to 25, according to the statement. The levels of antibodies in the vaccinated adolescents was higher than the levels in the adults.

Eighteen adolescents in the non-vaccinated group tested positive for Covid-19 during the trial, while nobody in the vaccinated group did, so the companies concluded that the vaccine was 100 percent effective at preventing symptomatic illness during the trial.

“It’s pretty impressive,” says Peter Hotez, co-director of the Center for Vaccine Development at Texas Children’s Hospital, to CNN’s Alisyn Camerota and John Berman. “Now on the other hand it’s 1,200 individuals and undoubtedly as you get to larger groups, we’re talking about millions of individuals, probably the 100 percent won’t hold up. But given the levels of virus neutralizing antibodies that we’re seeing in adolescents, it’s going to be a pretty damn good vaccine.”

BioNTech’s CEO and co-founder Ugur Sahin says in the statement the company hopes the vaccine will be available to adolescents in time for school to begin in the fall. But for younger children, it may take much longer to obtain FDA authorization because trials need to include long-term monitoring for a rare inflammatory condition, MIS-C, that has impacted children after they recover from an initial bout of Covid-19, Hotez tells CNN.

The press release did not address how the researchers identified cases of Covid-19, whether they tested for asymptomatic cases, or whether they looked for variants of the coronavirus.

"It would be useful to know how effective the vaccine is at preventing asymptomatic infection,” says Peter English, former chair of the British Medical Association’s public health medicine committee, in a statement. “Young people are less likely to have severe disease; and when they are infected, they are more likely to have asymptomatic infection, allowing them to transmit the disease to others.”

Georgetown University virologist Angela Rasmussen tells the New York TimesApoorva Mandavilli that the low numbers of confirmed Covid-19 cases—just 18, compared to 170 in the Phase III trial in adults—make it difficult to be specific about the efficacy results presented in the Pfizer-BioNTech statement. But the results are positive. Rasmussen says to the Times, “The sooner that we can get vaccines into as many people as possible, regardless of their age, the sooner we will be able to really feel like we’re ending this pandemic for good.”

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