Pfizer in late March released preliminary results from a vaccine study of 2,260 USA 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.
Pfizer's shot is now approved for use in people 16 years of age and older.
The vaccine was previously authorized for anyone 16 or older.
The country had started the COVID-19 vaccination drive on January 16 with two vaccines - Covishield (Oxford-AstraZeneca's vaccine manufactured by Serum Institute of India) and Covaxin (manufactured by Bharat Biotech Limited).
Canada is the first country in the world to sign off on giving shots to these younger age groups.
"After completing a thorough and independent scientific review of the evidence, the department determined that this vaccine is safe and effective when used in this younger age group", said Health Canada's chief medical adviser Dr. Supriya Sharma.
The two-dose Pfizer vaccine was the first COVID-19 vaccine to be authorized by Health Canada.
"There are some provinces that have already provided some vaccine to this age group, if they were children that were at high risk". COVID-19 vaccine sales contributed $3.5 billion in the quarter and are guided to be nearly $26 billion in 2021, above previous guidance of $15 billion and ahead of our $23 billion estimate. More than 34% of Canadians have received at least one dose.
The company has generally applied to Canada for approval around the same time but in this case Canada is ahead of the U.S. The U.S. Food and Drug Administration expects to authorize the vaccine for 12 to 15 year olds next week.
Kids studied had side effects similar to young adults, the company said, mainly pain, fever, chills and fatigue, particularly after the second dose.
Health Canada said it will require Pfizer-BioNTech to continue providing information to it on the safety, efficacy and quality of the vaccine in this younger age group to ensure its benefits.
Since the beginning of the pandemic, about 20 per cent of COVID-19 cases have been reported in people under the age of 19, she adds.