OTTAWA -- While U.S. President Joe Biden pledges that there will be enough COVID-19 vaccine supply for every adult in America by the end of May, Prime Minister Justin Trudeau says he’s not ready yet to say Canada’s immunization timeline will speed up, but he’s “very optimistic” it will.

“We are now fully back on track and even ahead of schedule in terms of where we were hoping to be for the end of March,” Trudeau said Wednesday, facing questions about Canada’s pace of immunization, in light of Biden moving up his country’s timeline.

What the prime minister seems to be waiting to see—noting the delivery shortages and delays Canada experienced in the first months of the mass vaccination campaign— is “if indeed, all the vaccines that we've contracted for are able to be manufactured and shipped in the right ways.”

For months, the federal government has stuck to its pledge that every Canadian who wants to be vaccinated, will be by the end of September. It’s a timeline that officials have indicated could accelerate should additional vaccines be approved and arrive in this country in the months ahead.

The uptick in supply has begun, with last week’s Health Canada authorization of the AstraZeneca vaccine, and could be given another shot in the arm in the weeks ahead if Johnson & Johnson’s single-dose vaccine is given the green light.

Asked whether he was concerned about the impact that the American economy likely fully reopening ahead of Canada’s might have, Trudeau noted the different pandemic experiences both countries have had and cautioned against comparing.

“It's possible that those timelines be moved forward, and we're certainly going to work closely with the provinces in order to try and get to that, to get vaccinations to Canadians as quickly as possible so that we can loosen and reopen as quickly as possible,” he said.

Should the U.S. have all the doses needed in that country by the end of May, it opens up questions as to whether larger numbers could be sent to Canada earlier. It’s something Trudeau said he’s spoken with Biden about generally, but there’s no concrete commitment that Canada would be in line to receive any potential surplus from the U.S.

Trudeau indicated that in his conversations with Biden he seemed “very open to helping out other countries,” once Americans were immunized, and said it’s a conversation that will continue.

The most recent COVID-19 vaccination timeline showed that at least 14.5 million Canadians will be able to be immunized by the end of June with Pfizer-BioNTech and Moderna doses, but that could increase up to 24.5 million Canadians if additional shots are granted regulatory approval.

The remaining millions of Canadians who are eligible to receive these vaccines would be left waiting until sometime between July and September.