Canada's vaccine advisory committee is recommending immediately suspending the use of the AstraZeneca-Oxford COVID-19 vaccine in Canadians under 55 following reports of rare but potentially fatal blood clots in Europe that appear to be connected to the shot.
The National Advisory Committee on Immunization (NACI) updated its guidelines to provinces and territories against the use of the vaccine for younger Canadians on Monday over safety concerns.
Health Canada said Monday that 300,000 doses of AstraZeneca vaccine have been administered and no cases of the rare blood clotting adverse events have been reported in Canada but that it was aware of additional cases that have recently been reported in Europe.
Quebec and Newfoundland and Labrador have suspended the use of the vaccine for anyone below the age of 55 while Prince Edward Island also halted its use of the shot in residents aged 18 to 29 who work directly with the public. Other provinces and territories are expected to follow.
"You cannot ignore the blood clots that have been associated with AstraZeneca globally," said Dr. Isaac Bogoch, an infectious diseases physician and member of Ontario's COVID-19 vaccine task force.
"It's not entirely clear what the true incidence of this is, but it does appear to be a rare event."
NACI previously recommended earlier this month that Canadians over 65 not receive the shot, despite emerging evidence from around the world demonstrating its ability to prevent severe COVID-19 in older adults.
But that guidance changed on March 16 after more real-world data on the vaccine's effectiveness was reviewed by NACI, and CBC News broke the story revealing documents on the federal government's plans to allow those 65 and older to receive it.
"What we need to have is continued confidence in our expert review panel that it's looking at these vaccines and deciding what is going to be best, safest and most effective for Canadians," said Alyson Kelvin, an assistant professor at Dalhousie University and virologist at the Canadian Center for Vaccinology in Halifax.
"This is a new vaccine to a new virus, it's really important that we're following all the data as closely as possible and as the vaccines are rolling out, we're understanding them more and reviewing what the guidance should be."
What led to Canada's decision to suspend AstraZeneca
The decision to halt the use of the vaccine in Canadians under 55 comes after the European Medicines Agency (EMA) investigated 25 cases of the rare blood clots out of about 20 million AstraZeneca shots given. It concluded on March 18 that the benefits from the vaccine far outweigh its possible risks, although a definitive link could not be ruled out.
But 18 of the cases in Europe were of an extremely rare type of blood clot called cerebral venous sinus thrombosis (CVST) — where veins that drain blood from the brain are obstructed and can potentially cause fatal bleeding.
The EMA said on March 18 at least nine deaths have been associated with the adverse events in Europe and the agency is continuing to investigate the situation.
Germany's medical regulator told The Associated Press on Monday it had received reports of 21 cases of rare blood clots in people who had recently received AstraZeneca's coronavirus vaccine.
The Paul Ehrlich Institute also said that seven people affected by the blood clots have died. It added that of the 21 cases reported in Germany until March 25, 12 also involved an abnormally low level of platelets in the patients' blood.
Nineteen of the 21 cases were in women ages 20 to 63, while two were in men ages 36 and 57. During the period covered by the reports, some 2.27 million first doses of the AstraZeneca vaccine were administered in Germany.
Bogoch said that the discovery of a potential connection with the vaccine to blood clots, particularly CVST, raised a "red flag" that "warrants further exploration."
"People should appreciate that not all blood clots are created the same," he said. "This is a very specific and particular method of blood clotting that likely has an association with the vaccine."
What Canadians need to know about the AstraZeneca vaccine
The federal health ministry said it would be issuing additional terms and conditions on the authorization of the vaccines from both AstraZeneca and India's Serum Institute, including requiring the manufacturers to conduct risk assessments by age and gender.
Health Canada had previously updated the vaccine's label with information on the rare blood clotting events.
Canadian health officials said during a press conference Monday the specific syndrome is being called Vaccine-Induced Prothrombotic Immune Thrombocytopenia (VIPIT) and that they are in contact with European officials about it.
They added that the Paul Ehrlich Institute reportedly said VIPIT has an incidence rate of about one in per 100,000, with a mortality rate of about 40 per cent, although more research is needed and that risk is reduced if treated early enough.
The Ontario COVID-19 Science Advisory Table released guidance on VIPIT and said Canadians should speak with a healthcare professional if they have the following symptoms between four and 20 days after vaccination:
Severe headache that does not go away.
Difficulty moving part of your body.
New blurry vision that does not go away.
Shortness of breath.
Severe abdominal pain.
New severe swelling, pain, or colour change of an arm or a leg.
Most of the incidents in Europe occurred within 14 days of receiving the AstraZeneca shot, and the majority were in women under the age of 55. It's worth noting that CVST is typically more common in women, particularly during and after pregnancy, while on birth control and hormone replacement therapy.
Germany and Italy resumed vaccinations with the shot on March 19, but France opted to vaccinate only those over 55 with it after discovering several cases of CVST. Denmark and Norway have suspended the use of the vaccine altogether for at least three weeks, while Sweden has resumed the use of the vaccine in those over 65.
"The real question here is, how common is it, and are there identifiable risk factors for this? That way, we could probably continue to use this vaccine in people with very, very low risks of having a blood clot and selectively vaccinate people who would benefit," Bogoch said.
"If there is that risk, we would hopefully have better data to support who we could safely and selectively vaccinate with this product."