Canada's National Advisory Committee on Immunization (NACI) now recommends expanding the use of the AstraZeneca-Oxford vaccine to all Canadians over the age of 30, but only when the benefits outweigh the risks of rare, serious post-vaccine blood clots.
The advisory body issued its latest guidance on Friday after reviewing new provincial data on the high level of risk currently posed in Canada by COVID-19.
Given the hot spots of infections across the country, and widely-circulating variants of concern, NACI said the age cut-off for the beleaguered AstraZeneca vaccine should be lowered to 30-years-old, with a few caveats.
The shot only makes sense for individuals if the "benefits outweigh the risks" associated with the blood clots that occur in rare instances post-vaccination, NACI concluded.
It should also only be given to those without contraindications — any health conditions that would heighten the risk of the vaccine causing someone harm — and if the individual does not want to wait for an mRNA vaccine.
"What we've said is that there should be individual choice," explained Dr. Shelley Deeks, NACI's vice-chair.
4 official cases of rare, serious blood clots
NACI's announcement came the same day Prime Minister Justin Trudeau got vaccinated with his first dose of AstraZeneca, making him the latest Canadian official to get the shot following weeks of controversy over the blood clotting concerns.
Right now in Canada, there are four official cases of vaccine-induced immune thrombotic thrombocytopenia (VITT), which is estimated to occur in one out of every 100,000 to 250,000 people vaccinated with the AstraZeneca-Oxford COVID-19 vaccine.
A similar condition has also been reported in the U.S., tied to use of the Johnson & Johnson vaccine.
WATCH | Prime Minister Justin Trudeau gets first dose of AstraZeneca-Oxford vaccine:
The mechanism behind the rare blood clotting condition isn't entirely clear, but the outcomes can often be dire — with traditional treatment methods, like the blood thinner heparin, actually making it worse.
The mortality rate of VITT is around 40 per cent, according to NACI, and it can present as serious clots in the veins that drain blood from the brain.
Because of this rare risk, Deeks said Canadians should be able to wait and receive an mRNA vaccine — those currently approved in Canada from Pfizer and Moderna — if they so choose.
"NACI continues to preferentially recommend authorized mRNA COVID-19 vaccines due to the excellent protection they provide, the absence of safety signals of concern and the acceptability of the vaccines by people in Canada," the advisory committee's latest statement reads.
But for anyone who wants to get a shot earlier, the AstraZeneca vaccine remains a "safe way to be protected," according to NACI chair Dr. Caroline Quach-Thanh.
'More and more' VITT cases expected
While all approved vaccines are deemed safe for use by Health Canada, the NACI officials did note additional cases of VITT could occur as more people get the AstraZeneca shot.
And, despite issuing earlier guidance that the AstraZeneca shot should go only to older adults, the advisory body now considers all age groups at equal risk of experiencing cases of VITT.
WATCH: NACI's Dr. Caroline Quach-Thanh discusses the committee's updated AstraZeneca vaccine recommendations:
"We're going to see more and more," Quach-Thanh said.
She said that as more cases are identified earlier and health-care workers become better acquainted with VITT, the outcomes and treatments should improve.
Hamilton, Ont.-based hematologist and Ontario COVID-19 Science Advisory Table member Dr. Menaka Pai agreed the early mortality rate should drop once physicians know what to watch out for, and what traditional treatments — including heparin — that they should avoid.
"It's not like a heart attack where every doctor has seen scores of them, and it's very automatic what we do," she said.
"This is an aggressive clotting disease, but in terms of how you manage it, it is actually very treatable. The tricky part is actually detecting it."
What's crucial, NACI officials say, is ensuring Canadians know the post-vaccination warning signs before consenting to an AstraZeneca shot, with symptoms including:
Shortness of breath
Chest or abdominal pain
Severe headaches or blurred vision
Skin bruising or a skin rash
Deeks stressed while these post-vaccination issues are a new concern, similar conditions have occurred under different circumstances.
"But we must remember: this is rare," she said.
Officials advise weighing benefits, risks
Rare as the clots may be, NACI made it clear Canadians have the right to choose their vaccine — and should take into account their personal risk level of contracting COVID-19 and experiencing a poor outcome from the illness.
Speaking at Friday's media conference, B.C.'s provincial health officer Dr. Bonnie Henry stressed COVID-19 itself causes higher rates of serious blood clotting, though the risk differs across age ranges.
In a province with high rates of infection, Henry said her stance is to get whichever vaccine is being offered first, since the risks posed by COVID-19 are heightened when transmission is so widespread.
So if you're in an area of lower transmission, and young and healthy — what then?
"If you're looking at NACI's recommendations and it seems confusing, go back to that really individual decision: what are my risks of taking the vaccine, and what are my risks of waiting and not taking it and getting COVID?" said Pai.
In a statement, the Public Health Agency of Canada (PHAC) said before getting the shot, Canadians should consider their risk of exposure to COVID-19, their risk of severe complications due to their age or underlying medical conditions, and the benefits of getting vaccinated sooner.
"We continue to be committed to providing information to support individuals in informed decision-making on vaccination," PHAC's statement continued.