May 10, 2021 6:37 PM EDT

On May 10, the U.S. Food and Drug Administration (FDA) extended authorization of the Pfizer-BioNTech COVID-19 vaccine to 12- to 15-year-olds. It’s the first COVID-19 shot authorized for this younger population.

“I cannot tell you how many people have been anxiously awaiting this day to get their kids vaccinated,” says Dr. Flor Munoz, a pediatric infectious disease specialist at Texas Children’s Hospital and Baylor College of Medicine, and a member of the infectious disease committee of the American Academy of Pediatrics.

The green light was based on review of data the two companies released in March showing that two doses of their vaccine provided similar protection from COVID-19 disease among this age group as it did for adults. Among the more than 2,200 teens in the study group the FDA reviewed, 16 developed COVID-19—none of them were in the vaccinated group. The companies’ studies found that levels of virus-fighting antibodies were on average higher among the 12- to 15-year-olds that got the vaccine than among vaccinated 16- to 25-year-olds in previous studies.

“This is part of the totality of getting our country protected against COVID-19, which is just waiting around the corner to come have another wave if we don’t get a sufficient degree of vaccination,” said Dr. Peter Marks, director of the Center for Biologics Evaluation and Research at the FDA, during a briefing discussing the decision.

The authorization was based on a so-called “bridging” study, in which researchers used data from the previous study in adults to set thresholds for safety and efficacy. Building off of the success of the adult studies enabled the scientists to enroll some 2,000 12- to 15-year-olds, rather than the tens of thousands of adults that the earlier studies required.

“The goal was that if we could show that the immune response in 12- to 15-year-olds was as good or better than that in 16- to 25-year-olds, then that would make the argument that the 12- to 15-year-olds were getting the same type of antibody response, and that they should enjoy the same level of efficacy,” says Dr. Bill Gruber, senior vice president of vaccine clinical R&D at Pfizer. “It turns out the antibody response was even better among the 12- to 15-year-olds so the public can rest assured that the [vaccine] protection should be as high for them as for adults.”

Now that the shot is authorized, the next step is to get it into arms. The Biden Administration said last week it was ready to start shipping more Pfizer-BioNTech vaccines directly to pediatricians’ offices, where many teens are treated, to make it convenient for them to get vaccinated. To accommodate the potentially smaller number of doses more doctors will need, Pfizer-BioNTech will begin shipping its vaccine in smaller sized trays in the thermal containers that can keep the doses properly chilled.

Some doctors, however, are still seeing some hesitancy among parents in vaccinating their kids. “I would say there is a 50-50 split between parents who can’t wait to give their kids the vaccine, and parents who are slightly or more hesitant,” says Dr. Allison Messina, chief of infectious diseases at Johns Hopkins All Children’s Hospital. Seeing other parents safely vaccinate their kids is helping to convince the latter group, she says, and seeing how much vaccination can contribute to helping their teens resume normal life is also key. The authorization should, for example, help schools and summer camps be safer environments if more teens get the shot.

While, overall, younger people tend not be as affected by COVID-19 as older people are, as more of the older population is vaccinated and protected, new infections are increasing among younger people, with public health experts saying that the majority of hospitalizations in nearly half of states are among people under age 65. Public health officials hope that vaccinating more teens will help to contain spread of the virus, especially during youth sports, school events and even family gatherings. “The more people are vaccinated in a school setting, the safer everyone is going to be from the disease,” says Messina. Munoz notes that many families may now have adults who are vaccinated but teens and young children who are not, and the teens could potentially be exposing the younger children, who aren’t eligible to get vaccinated yet, to infection. “If you can protect as many people as possible in the household, then you are also indirectly protecting those who cannot yet be vaccinated by providing fewer opportunities for the virus to come in,” she says.

Since the FDA extended the authorization to 12- to 15-year olds, the Centers for Disease Control’s Advisory Committee on Immunization Practices will meet on May 12 to make the official recommendation for recommending the vaccine for this age group.

Pfizer and BioNTech are continuing to study their vaccine among even younger children. Gruber says the scientists will be looking to see if lower doses can be used in those aged six months to 11 years.

Contact us at letters@time.com.

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