TORONTO -- Health Canada has extended the expiry date of roughly 45,000 AstraZeneca doses that were supposed to expire on Monday by a month, according to the Ontario government.

On Saturday, the Ministry of Health released a statement stating that Health Canada had extended the shelf life of specific lots of AstraZeneca vaccines from six months to seven months, following the review of stability data.

“Vaccine doses with an original expiry date of May 31, 2021 can now be used until July 1, 2021,” a spokesperson from the Ministry of Health said in a statement.

"On May 27, 2021, Health Canada received a submission from AstraZeneca that included product stability and mathematical modelling data that demonstrated that the quality, safety and efficacy of the two lots would be maintained for an extra month, for a total of up to seven months," the statement read.

"This change will ensure that provinces and territories are able to use up their existing inventory and provide Canadians access to much needed doses of the vaccine."

The news comes as pharmacists and doctors have been rushing to administer approximately 45,000 doses that were set to expire on Monday.

About 90,000 people who got their first shot of AstraZeneca between March 10 and March 19 became eligible to book their follow-up appointment on Tuesday.

These individuals participated in the initial rollout of the AstraZeneca vaccines at participating pharmacies in Toronto, Windsor and Kingston.

A list of eligible pharmacies administered second doses can be found on the provincial government’s website. Primary care offices and pharmacies may also be reaching out to eligible Ontarians.

Speaking to CP24 Saturday afternoon, Dr. Dirk Huyer, a member of the vaccine distribution task force and coordinator of the province's outbreak response, said he is pleased with the decision.

"I think Health Canada is driven by safety. And they're driven by following principles of appropriate, safe vaccine. I can't speak to their specific process, but they carefully evaluate all vaccine submissions and all vaccine products to ensure that it's the safest possible," Huyer said.

When asked about concerns about the timing of the extension, Huyer said he is confident that the agency looked at all the data and other information provided by the manufacturer in evaluating the vaccine's expiration.

"I think Health Canada has a full understanding of AstraZeneca and all the vaccines. They're regularly monitoring, regularly paying attention and evaluating the safety," he said. "We have a robust safety surveillance process within Ontario and Canada," Huyer said.

The province suspended use of the AstraZeneca vaccine earlier this month due to an increased risk of rare blood clots, but 10 days later decided to resume administering the shot for second doses so that vials sitting in the fridge didn’t expire

This week, pharmacists and doctors have been scrambling to get their hands on the remaining doses to administer them before Monday.

Many residents were left feeling frustrated about the lack of clarity surrounding which pharmacies were offering the second shot.

“We started to receive vaccine in the Toronto pharmacies not until Thursday afternoon, into the late evening, and then all throughout Friday we’ve had top-ups because it’s slowly being released from the distributor as they go through that QA (quality assurance) process and checking of temperature logs,” Ontario Pharmacists Association CEO Justin Bates told CP24 Saturday morning. Bates said pharmacies are expecting to receive more vials later on Saturday and on Monday.

Before Health Canada announced the extended expiry date, Bates said he was worried about some doses spoiling as a result of the temporary pause on administering the vaccines earlier this month.

“The science has evolved and that was part of why we wanted to do the pause a couple of weeks ago with the first-dose vaccinations. So that has led to some of this. There’s no question that the delay in getting this out into pharmacies increases the prospect of having some wastage,” Bates said.

“But we’re prepared to do whatever we need to do in terms of extending hours. Many pharmacies do close on Sundays and they will remain open to accommodate patients [..],” he added.

Toronto pharmacist Mina Maseh says Health Canada needs to properly explain its decision to extend the expiration date of the AstraZeneca vaccine. He said he's been getting a lot of questions from customers wanting to take the vaccine, but who are hesitant due questions around the expiry date.

"We're a little bit frustrated. Everything just keeps coming out of the left field. Nobody's really telling us anything until it goes on the news," Maseh said in an interview with CP24.

"Health Canada, I'm sure they did their proper due diligence and the regulatory inspections, but unless they're going to go up to the public and explain it, I don't know how they expect healthcare professionals to be fielding all these questions," he continued.

Maseh urged the federal agency to step up and provide pharmacists with an explanation so that they can confidently relay it to their patients, he said.

"Let's not put more doubt in people's eyes and people's minds because they were already doubtful," he said, "Why are we causing more hesitancy for more patients right now with a last-second announcement?"

"If they're not going to provide [the data], we can't do anything. We're not going to put even one patient at risk of something that may not have been properly inspected," Maseh continued.

This weekend, 162 pharmacies in Toronto, Kingston and Windsor are expected to be administering second doses of AstraZeneca.

On Friday, the government released its second dose strategy and said that AstraZeneca vaccines could be administered at 10-week intervals for those who received their first dose between March 10 and 19. Meanwhile, second doses for everyone else who received a first shot of AstraZeneca will continue with a 12-week interval.

The province is not offering AstraZeneca shots to anyone else as a first dose, except in very limited circumstances where someone is allergic to the approved mRNA vaccines being administered in Ontario.

Ontario received 254,500 doses of AstraZeneca the week of May 17, which will support second doses at the 12-week interval.

- with reporting from Beatrice Vaisman