Pfizer Inc. and its partner BioNTech SE said they would ask regulators in the U.S. and elsewhere to allow use of their COVID-19 vaccine in adolescents ages 12 to 15.

The companies said in a statement that they had requested that the U.S. Food and Drug Administration expand the vaccine’s emergency-use authorization and that they plan to request similar rulings from other regulators worldwide in coming days.

If the requests are granted, it could pave the way for many more schoolchildren to be vaccinated before the next school year.

Shares of Pfizer gained 1.1 per cent to US$36.36 at 1 p.m. in New York, while U.S.-traded shares of Germany-based BioNTech climbed 5 per cent.

A study released last month found that the vaccine was 100 per cent effective in preventing COVID illness in a final-stage trial in children from 12 to 15. The study used the same dose and two-shot regimen that is now used in adults. The vaccine is authorized in the U.S. for people ages 16 and older.

In the study of 2,260 adolescents, the vaccine produced antibodies against COVID-19 that exceeded the level seen in vaccinated young adults, Pfizer and BioNTech said in a statement on March 31. All 18 cases of COVID-19 were in adolescents who were administered a placebo, the companies said. Side effects were consistent with those experienced by people ages 16 to 25.

In people age 16 and up, the vaccine was 95 per cent effective at preventing symptomatic disease, according to the initial results from its phase 3 trial. It remained 91 per cent effective through six months after the second shot, according to recently released long-term results from the same trial.

In March, both Pfizer and the maker of the other mRNA vaccine against the coronavirus, Moderna Inc., began trials for their vaccines in children under age 12.

Moderna is also studying its vaccine, which is now authorized for people 18 and older, in adolescents ages 12 to 17. That trial is fully enrolled, and is on track to yield updated data in the middle of the year, Moderna has said.