The US pharmaceutical firm Pfizer and its German partner BioNTech say they have found their coronavirus vaccine to be effective for children between the ages of 12 and 15.
The Pfizer-BioNTech vaccine is currently authorized for use in those aged 16 or older.
The two companies released on Wednesday the results of clinical trials on 2,260 12- to 15-year-olds in the US to test the vaccine's safety and efficacy.
In the trials, they said 18 children among 1,129 who were given placebos developed symptoms of COVID-19, but none among the 1,131 who were vaccinated did so.
The companies said side effects were largely the same as those seen in people between ages 16 and 25.
Pfizer has begun clinical trials on even younger children, between six months to 11 years old.
Another US firm, Moderna, is testing its vaccine on those aged six months up to 17.
The University of Oxford, which developed a vaccine with the British pharmaceutical firm AstraZeneca, is carrying out clinical trials on 6- to 17-year-olds.
Pfizer and BioNTech plan to submit their data to the US Food and Drug Administration and the European Medicines Agency to apply for emergency use of their vaccine in children.