THE European Commission on Friday authorized Pfizer and partner BioNTech SE's COVID-19 vaccine for use in children as young as 12, paving the way for a broader roll-out in the bloc after similar clearances in the United States and Canada.

The decision comes after European Medicines Agency (EMA) backed the use of the vaccine in 12- to 15-year olds earlier in the day.

The agency's endorsement came weeks after it began evaluating extending use of the vaccine to include that age group. The vaccine is already being used in the European Union for those aged 16 and above.

The EMA said two doses of the vaccine, branded as Comirnaty, were required in the 12-15 age group and should be administered with an interval of at least three weeks, the same as for adults, adding that it was up to individual EU states to decide if and when to offer the vaccine to teenagers.

Distribution and administration of the vaccine by the EU member states will continue to be determined according to the populations identified in the EU and as per national guidance, Pfizer and BioNTech said.

Germany on Thursday laid out plans to offer shots to 12-year-olds from June 7, pending the EMA's verdict. Italy has also said it is preparing to extend its campaign to over 12-year olds.

Inoculating children and young people is considered a critical step toward reaching "herd immunity" and taming the pandemic, and Japan on Friday joined the countries with a go-ahead for Comirnaty in 12-year-olds.

Youngsters have been much less likely to suffer severe disease, with many experiencing no symptoms, allowing them to unwittingly transmit COVID-19 to others.

However, giving vaccines to younger people in affluent countries while many parts of the world await doses for older and more vulnerable people has raised concerns.

Pfizer and BioNTech in March unveiled trial data showing their vaccine offered 100% protection against the infectious disease in a trial with 2,260 adolescents aged 12 to 15. It was also well tolerated.

The pair managed to steal a march on other drugmakers, including AstraZeneca, Moderna and Johnson & Johnson, who are working on vaccines for children, some as young as six months.

The shorter duration of safety monitoring in trials so far in the 12-15 age group compared with older cohorts was not a concern, said Marco Cavaleri, EMA's head of health threats and vaccines strategy.

"Based on the experience that we've gathered with many other vaccines throughout the years is that ... what we see with young adults is also seen in adolescents," he told a news briefing, when asked about side effects. He added that monitoring would intensify as vaccine recipients become younger in future.

Others have voiced caution, however, such as a member of Germany's influential vaccine advisory committee Stiko. Paediatrics professor Ruediger von Kries has said the vaccine might only be called for in children with particular health risks, citing a lack of data on long-term side effects.

At the briefing, EMA also said that reports of cases of an inflammation of heart muscles following vaccination with Comirnaty were no cause for concern as they continued to happen at a rate that typically affected the general population.