OTTAWA -- Canada's promised spring supply of COVID-19 vaccines grew Tuesday with millions of additional doses now expected to arrive from three different suppliers before Canada Day.

But the news was tempered by ongoing concerns about the Oxford-AstraZeneca vaccine, and signs in much of the country that the pandemic still has a lot more misery to unleash.

"We're entering the final stretch of this crisis," Prime Minister Justin Trudeau said at a news conference in Ottawa. "We just need to stay strong, a little longer. More and more vaccine doses are coming every week. So there's reason to be hopeful."

Trudeau said Pfizer and BioNTech will send another five million doses of their mRNA vaccine to Canada in June, bringing their total shipments in the spring to 17.8 million. The company is expected to ship more than one million doses a week in April and May, and more than two million every week in June.

Procurement Minister Anita Anand added that Canada now expects 4.4 million doses of the AstraZeneca vaccine by June 30, and said the first shipments of Johnson & Johnson's single-dose vaccine are set to arrive at the end of April. She doesn't know yet how many doses will be in that first shipment.

Even without J&J, and barring any unexpected interruptions in production or export of vaccines, Canada is in line to get more than 44 million doses before Canada Day.

That should mean all adults over 18 will be offered a vaccine faster, and that the wait for a second dose may not be as long as the current four months.

Canada needs about 31 million doses to offer at least one shot to every adult.

Medical experts across Canada stepped up efforts to combat vaccine hesitancy Tuesday, following the latest news that every province and territory will stop using the AstraZeneca vaccine for people under age 55, pending further analysis of the risks it might pose.

Health Canada requested more analysis from the company Monday due to more reports from Europe about blood clots developing in a small number of patients after they were vaccinated with AstraZeneca. Most of those patients were women under the age of 55.

Dr. Theresa Tam, the national chief public health officer, said she knows this is another difficult development in the seemingly never-ending twists and turns of the pandemic.

But she said the system is working the way it was intended and that people can be confident in the vaccines Canada has approved.

No blood clots linked to the vaccine have been found in Canada. About 309,000 doses have been given in Canada to date from the initial shipment of 500,000 two weeks ago. Many provinces initially reserved those doses for people in their 50s and early 60s.

Alberta's medical officer of health Dr. Deena Hinshaw said Monday that Alberta got 58.500 AstraZeneca doses and only 900 went to people under 55.

Others, like Prince Edward Island, which were using AstraZeneca entirely on younger adults, have stopped its use entirely for the moment.

Tam warned that even as vaccinations ramp up, Canadians need to be aware that COVID-19 is spreading faster in many parts of the country, driven by variants of the virus that are not only more contagious but are making people sicker.

She said hospitalizations are up six per cent in the last week and the number of patients needing critical care is up 14 per cent. There are 4,600 new COVID-19 cases a day on average in Canada now, compared to 3,600 a week ago.