Questions remained Wednesday about the future of the Oxford-AstraZeneca vaccine in Canada as Manitoba limited use of the shot and Ontario said it was deciding how it would use an incoming shipment reserved for second doses.

Ontario -- which has stopped administering AstraZeneca as a first dose over concerns about a rare clotting disorder -- announced it will receive a quarter-million doses of the vaccine next week but is still reviewing when it will open up appointments for second doses.

Alberta, too, has stopped offering the shot to those who have yet to be vaccinated, but cites a lack of supply for the move.

Manitoba, meanwhile, announced Wednesday that it plans to offer first doses of the AstraZeneca vaccine only to those who might not be immunized at other sites.

Most doses will be held for second shots for people who received an AstraZeneca vaccine in the first go-around, the province said, "in response to ongoing evidence and supply." Manitoba said it will receive about 20,000 doses of AstraZeneca in its next shipment.

The uncertainty over AstraZeneca has rankled some who already received their first dose of that vaccine and are undeterred by the risk of vaccine-induced thrombotic thrombocytopenia, also known as VITT.

A group of scientists advising the Ontario government has pegged the rate in Canada at 1 in 55,000 doses of AstraZeneca vaccine as of May 8, though it noted that some presumptive cases were still being investigated.

More than two million Canadians have received AstraZeneca and 17 have been confirmed to have VITT. Three women have died.

Alison Meek, who received her first dose of AstraZeneca last week, said she'd take a second shot of the same vacine "in a heartbeat."

"I would have taken any of the ones that was offered. I think it is important not just for our own health, but to protect those around us. I think it's needed to get out of this -- these lockdowns that we're in," said Meek, who lives in London, Ont., and teaches history at Western University.

She said she had muscle aches and a fever after the shot but is happy with her decision.

"I have no regrets whatsoever, and would happily take the second dose," Meek said.

Ontario currently has roughly 50,000 doses of the AstraZeneca shot left, some of which are due to expire in the coming weeks.

"I hope that they're not going to be dumping those down the drain," Meek said.

Toronto writer Emily Saso, 40, also stands by her decision to get the AstraZeneca shot in late April to guard against the risks of her husband bringing the COVID-19 virus back home from work.

But Saso said the shifting messages surrounding the AstraZeneca vaccine have done little to quell her longstanding fear of blood clots.

"It was definitely a failure of communication," she said. "And that added to my anxiety, which was already high."

Experts have noted that the risk of clotting is much higher among people diagnosed with COVID-19 than those who received the AstraZeneca shot.

Health Canada's chief medical adviser has said that from an authorization perspective AstraZeneca's benefits against COVID-19 still outweigh the rare risk of VIIT.

As questions over the use of AstraZeneca continue to swirl, however, health officials in all provinces are now watching for the results of a British study on mixing and matching vaccines.

Data could come on AstraZeneca and Pfizer as early as this week, with many health experts expecting very positive results from combining two different vaccines.

This report by The Canadian Press was first published May 12, 2021.