Pfizer and BioNTech on Wednesday released data showing their Covid-19 vaccine is highly effective at preventing symptomatic cases of Covid-19 among adolescents ages 12 to 15.

Is Pfizer's vaccine safe and effective? Our 8 biggest questions, answered.

Pfizer/BioNTech's vaccine effective among adolescents

Pfizer in a release announced the new data from a Phase 3 trial in the United States. The trial involved 2,260 adolescents ages 12 to 15 with or without prior evidence of a novel coronavirus infection. Of the participants, 1,131 received two doses of Pfizer/BioNTech's vaccine three weeks apart, and 1,129 participants received a placebo.

Webinar series: 'Stay Up to Date' on the latest with Covid-19

Pfizer in the release said the vaccine "demonstrated 100% efficacy and robust antibody responses, exceeding those recorded earlier in vaccinated participants aged 16 to 25 years old, and was well tolerated" in the trial.

According to the release, no cases of symptomatic Covid-19 occurred among adolescents who received the vaccine. In comparison, 18 cases occurred among participants who received a placebo, the release stated.

Pfizer said the vaccine also produced strong antibody responses among a subset of participants one month after they had received their second vaccine dose. According to the release, the vaccine generated antibody levels among the subset considered "non-inferior" to the levels seen among participants between the ages 16 and 25 in previous studies. Specifically, the data showed the vaccine "elicited SARS-CoV-2–neutralizing antibody geometric mean titers (GMTs) of 1,239.5" among the subset, compared to 705.1 GMTs among participants ages 16 to 25 years old in a previous analysis.

Further, Pfizer said the vaccine "was well tolerated, with side effects generally consistent with those observed in participants" ages 16 to 25. Although Pfizer didn't provide more details on the vaccine's side effects, previously released data on 100 participants ages 12 to 15—which Pfizer and BioNTech released in December as part of FDA's review of the vaccine—showed 20% of participants reported fever after receiving their second vaccine dose, compared with none of the participants in the placebo group. In addition, more than 25% of participants reported experiencing chills, compared with less than 10% among those who received a placebo.

What's next?

The data released Wednesday has not yet been peer-reviewed nor published in a scientific journal, the New York Times reports. However, Pfizer said the companies intend to submit the data for scientific peer review for potential publication.

Good? Bad? Ugly? We've updated our take on what's next for the epidemic.

Currently, Pfizer/BioNTech's vaccine is authorized for emergency use among people ages 16 and older. However, Pfizer said the companies plan to submit the new data to FDA "in the coming weeks" to expand their emergency use authorization to include adolescents ages 12 and 15.

Pfizer CEO Albert Bourla in the release said the companies hope to begin vaccinating adolescents in this age group before the start of next school year.

Reaction

Many experts celebrated the Pfizer's new data.

"Oh my god, I'm so happy to see this—this is amazing," said Akiko Iwasaki, an immunologist at Yale University. Iwasaki said if the vaccine's performance among adults was considered an A-plus, these results were "A-plus-plus." For example, she noted the data shows adolescents are "getting even better [antibody] levels from the vaccine" than young adults, which, she said is "really incredible."

Angela Rasmussen, a virologist affiliated with Georgetown University, said the low number of infections recorded in the trial make it difficult to make specific claims about the vaccine's effectiveness in the population at large, "[b]ut obviously, it looks good for the vaccine if there were zero Covid-19 cases among the vaccinated people."

However, Iwasaki and other experts warned that the vaccine may be less effective against some of the new variants of the coronavirus circulating in the United States.

All 50 states announce plans to expand vaccine eligibility

The new data comes as all 50 states have announced plans to expand their Covid-19 vaccine eligibility to all their residents ages 16 and older, CNN reports.

Currently, Pfizer/BioNTech's vaccine is the only one authorized by FDA for people ages 16 and older. Vaccines developed by Moderna and Johnson & Johnson are authorized for adults ages 18 and older (Herper, STAT News, 3/31; Saric, Axios, 3/31; Mandavilli, New York Times, 3/31; Morello, Politico, 3/31; Hopkins, Wall Street Journal, 3/31; Aspegren/Bacon, USA Today, 3/31; Howard, CNN, 3/30).