Canada's health regulator has authorised Pfizer's COVID-19 vaccine for ages 12 to 16, a person familiar with the decision the told the Associated Press on Wednesday.

The official spoke on condition of anonymity as they were not authorized to speak ahead of the upcoming announcement.

The U.S. Food and Drug Administration is also expected to authorize Pfizer's vaccine for young by next week, setting up shots for many before the beginning of the next school year. The announcement comes barely a month after the company found that its shot, which is already authorized for those age 16 and older, also provided protection for the younger group.

Pfizer in late March released preliminary results from a vaccine study of 2,260 U.S. volunteers ages 12 to 15 showing there were no cases of COVID-19 among fully vaccinated adolescents compared with 18 among those given dummy shots.

Kids had side effects similar to young adults, the company said. The main side effects are pain, fever, chills and fatigue, particularly after the second dose. The study will continue to track participants for two years for more information about long-term protection and safety.

Vaccinations have ramped in Canada in months and expects to receive at least 10 million vaccines this month. More than 34 per cent of Canadians have received at least one dose.