OTTAWA -- The panel of medical experts advising the federal government on vaccination has now expanded its recommendation for the use of the AstraZeneca vaccine to include people 65 years of age and older.

The National Advisory Committee on Immunization (NACI) issued new advice Tuesday morning stating that the two-dose viral vector vaccine can and should be given to seniors.

Since the AstraZeneca vaccine's initial approval for use in Canada last month, NACI says it looked at three real-world studies that justify expanding its advice to include those 65 and older.

Those studies showed that the AstraZeneca vaccine is safe and effective “particularly against severe COVID-19 disease and hospitalization” in older adults including those who are 80 and older with comorbidities.

Earlier this month, NACI initially recommended against administering the AstraZeneca vaccine to Canadians 65 years of age and older, and said they should be prioritized for the mRNA Pfizer-BioNTech and Moderna vaccines because there was stronger evidence of their efficacy in that age group.

NACI is still recommending the mRNA vaccines be prioritized for use in those at higher risk of exposure, severe illness, and death.

The initial suggestion to hold off on administering this vaccine to people older than 65 was at odds with Health Canada’s February regulatory approval of the vaccine. Health Canada has said that the AstraZeneca vaccine has an efficacy of 62.1 per cent among people 18 to 64 years old.

“It's not that we're flip-flopping, it's just that we try to monitor the evidence,” said NACI chair Dr. Caroline Quach-Thanh during a briefing, when asked to address the possible impact on vaccine confidence from changing the guidance in such a short timeframe.

“It's always easier if Health Canada and NACI agree, but it doesn't have to be. It’s not the first time it doesn’t,” she said, noting that the new studies informing their current position came to light following their initial guidance.

The NACI panel does not impose rules around vaccination. It only offers recommendations, which then allow provinces to tailor their own vaccination rollout plans to fit their needs.

The group says it will keep monitoring any new data from ongoing clinical trials and real-world evidence of the effectiveness of all vaccines currently approved byHealth Canada, and will further revise its recommendations as needed.

NACI’s changed guidance was welcomed by members of the medical community who are pushing to get as many Canadians vaccinated as quickly as possible, but are confronted by patients’ concerns about the AstraZeneca vaccine.

“The efficacy in terms of real world data shows that it is working, and the sooner we get shots in arms, the better it will be,” said Dr. Sandy Tecimer, clinical lead at Prince Edward Medical in Toronto in an interview on CTV News Channel.

However, Ontario Premier Doug Ford voiced his frustration with having to keep up with NACI’s continuously evolving advice.

“I can't begin to tell you the logistics behind it. It just messes everything up to be very frank with you. It's good news that they can you know, can go older than 65 but man, we have everything set up, get everyone lined up, and all of a sudden without notice today, now we can move the goalpost again,” Ford told reporters. “So now we have to change everything. It's not easy.”

HEALTH CANADA ON CLOT CONCERNS

Over the last few days several European countries have suspended use of the AstraZeneca vaccine following reports of blood clots in some recipients, despite European regulators indicating that there’s no evidence that the vaccine is to blame.

AstraZeneca has also said that a “careful review” of more than 17 million people who’ve received their vaccine in the U.K. and Europe found “no evidence” of an elevated blood clotting risk in any batch, or age group.

On Tuesday, Quach said NACI is monitoring the adverse events, but noted it’ll be up to Health Canada to advise whether Canada would pause the use of this vaccine. So far, the federal health agency continues to stand by its authorization of the AstraZeneca vaccine and says that the risk of contracting COVID-19 outweighs any potential complications.

“Health Canada is actively monitoring the ongoing situation in Europe… Based on the information that Health Canada has reviewed, the number of cases of thromboembolic adverse events at this point in time are lower than the rates that would be expected in the population that has been vaccinated with the AstraZeneca vaccine,” said Health Canada director Marc Berthiaume on Tuesday.

“We are aware of those cases, we are in direct communication with the European Medicines Agency… we are looking to get additional information about the case,” said Berthiaume, adding that more information will be made available on Thursday during an international meeting about these reports of adverse effects.

“At this point in time based on the information that has been distributed by and reviewed by Health Canada, there is no safety concern… but we're actively looking into the issue,” he said.

Further, Chief Public Health Officer Dr. Theresa Tam noted in a later press conference that, to date, there have been no unexpected vaccine safety issues identified in Canada.

Tecimer said her medical facility is nevertheless getting “called nonstop” with questions about the AstraZeneca vaccine. “So far the event rates of the clots from the vaccine are not higher than the event rates that we see in real life of blood clots. And we know that when you're infected with the COVID virus your risk of blood clots increases significantly, so we are encouraging patients not to hold back.”

Canada is scheduled to receive 23.9 million doses of the vaccine, with the first 500,000 doses already being administered across the country.

With files from CTV News’ Nicole Bogart and Ben Cousins