Canada's Ontario province, its most populous and with its most Covid infections, announced Thursday it is lowering the eligibility age for Covid boosters from 70 to 50 years old.
These third shots will be available starting December 13, the government said in a statement, adding that it plans in January to further expand eligibility for booster doses "based on age and risk."
"Achieving the highest vaccination rates possible remains our best tool to protect us, reduce the risk of Covid-19 transmission, and fight the significant surge of new cases and the new Omicron variant," Ontario's chief public health officer Kieran Moore said.
Ontario has recorded 620,000 Covid infections or more than one-third of Canada's total.
Alberta in the west is also lowering the eligibility age for booster shots to 60 years starting December 6, and said it is planning to soon open up third shots to everyone under 18 years, but did not specify a timeline.
Prime Minister Justin Trudeau this week said there will be sufficient supplies of booster shots.
"We have lots of vaccines for boosters in Canada," he told reporters on Wednesday. "We're receiving more into the new year. We are fine in terms of quantity."
Canada's national advisory committee on immunization currently recommends booster shots for high-risk groups, including those over 70 years or older, at least six months after their second dose.
According to the latest government data, almost 90 percent of Canada's population 12 years and older, or 30 million people, have received at least one Covid vaccine jab. Eighty-six percent are fully vaccinated.