Canada has secured tens of millions of COVID-19 booster doses to contain the virus in the years ahead, and a new federal forecast is offering hope that summer could bring a reprieve from lockdown restrictions if 75 per cent of Canadians get their shot.

Prime Minister Justin Trudeau announced Friday that Pfizer has agreed to supply 35 million booster doses next year, and 30 million in the year after.

The deal includes options to add 30 million more in both 2022 and 2023, and an option for 60 million doses in 2024, Trudeau said, adding that his government is in talks with other vaccine manufacturers about their plans for follow-up shots.

Boosters are expected to be an important part of long-term COVID-19 immunization as the virus continues to mutate, similar to how the flu shot is altered every year to be effective against the most dominant strain.

“Canadians expect us to be ready for whatever happens, and there is certainly a hope that booster shots might not be necessary,” Trudeau said in a televised address. “But we are much better off to ensure that we are prepared in case they are.”

The prime minister, his wife Sophie Gregoire-Trudeau and Health Minister Patty Hajdu each received a shot of the Oxford-AstraZeneca vaccine Friday in a political show of confidence, and soon afterwards a national advisory panel recommended the brand be made available to those as young as age 30.

Meanwhile, Canada's top public health doctor presented new modelling suggesting that a recent raft of restrictions may be reining in the variant-driven surge in infections, but said the outlook for summer hinged on the success of the vaccine rollout.

Dr. Theresa Tam said the projections suggest some hot-spot regions may be able to emerge from lockdown in time for people to take full advantage of the warm weather.

But for that to happen without overwhelming hospital capacity, at least 75 per cent of Canadian adults must receive their first shot, including 20 per cent who would be fully vaccinated.

“These models give us hope, illustrating that there is a safe way to lift most restrictive public health measures,” Tam told reporters. “This is why it is so important to roll up our sleeves and get vaccinated.”

Tam estimated Canada could reach this goal around mid-July to August but said that depends on whether vaccine shipments arrive on schedule.

Nearly 30 per cent of Canadian adults have received at least one COVID-19 shot, said Tam.

Procurement Minister Anita Anand said Canada is set to receive roughly 1.9 million vaccines over the next week. That includes 1 million doses from Pfizer, 650,000 from Modern and 300,000 from Johnson & Johnson.

While there are signs the third wave is ebbing, Tam noted that average COVID-19 case counts have more than doubled over the past month, with upwards of 8,400 infections reported daily over the last week.

Similarly, hospitals and intensive-care units have been treating at least twice as many COVID-19 patients since late March, said Tam. Over the past week, there was an average of 4,100 hospitalizations, including 1,200 in critical care.

But Tam said there's reason for hope due to Canada's declining reproduction rate, which represents how many people are infected by each new case.

This measure has fallen below the key threshold of one for the first time in weeks, meaning the rate of transmission is trending downwards.

Tam said hard-hit provinces including Ontario, Quebec and British Columbia have made strides in driving down infection rates, but warned that continued vigilance will be critical to maintaining progress.

Ontario reported 4,505 new cases of COVID-19 and 34 more deaths linked to the virus on Friday as Toronto and Peel Region were allowed to begin ordering the temporary closure of some businesses to control workplace outbreaks.

Pregnant individuals in the province became eligible for COVID-19 vaccines in light of new information showing they had a high risk of severe illness from the virus.

The province also reported its first case of a rare blood clot in a person who received the Oxford-AstraZeneca COVID-19 vaccine. It's the fourth case of the rare clotting condition in Canada out of more than 1.1 million AstraZeneca doses administered across the country.

Earlier this month, Health Canada concluded that very rare blood clots may be linked to the vaccine but reaffirmed that the benefits of an AstraZeneca shot outweigh the risk.

On Friday, the National Advisory Committee on Immunization recommended people 30 and older can get a shot of the Oxford-AstraZeneca vaccine if they do not want to wait for an alternative.

The committee initially recommended a pause on giving AstraZeneca shots to those younger than age 55 out of an abundance of caution.

Some provinces had preempted the committee's updated advice by offering AstraZeneca shots to people over 40, given the current spread of the virus.

This report by The Canadian Press was first published April 23, 2021.