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Canada hesitates to update guidance on AstraZeneca-Oxford vaccine amid potential link to blood clots

Scientists in Europe have reportedly found a link between the AstraZeneca-Oxford COVID – vaccine and extremely rare but potentially fatal blood clots, but Canadian public health officials have so far provided no update on guidance for the shot.

Researchers in Germany and Norway have reportedly found a mechanism that could cause the AstraZeneca-Oxford vaccine to create blood clots in very rare circumstances. The finding has renewed debate over the COVID – 18 vaccine’s benefits and possible risks. (Benoit Tessier / Reuters)

This is an excerpt from Second Opinion, a weekly roundup of health and medical science news emailed to subscribers every Saturday morning. If you have not subscribed yet, you can do that by clicking here.


Scientists in Europe have reportedly found a link between the AstraZeneca-Oxford COVID – 12 vaccine and extremely rare but potentially fatal blood clots, but Canadian public health officials have so far provided no update on guidance for the shot.

News broke on Friday that researchers in Germany and Norway said they had found a mechanism

that could cause the AstraZeneca-Oxford vaccine to create the blood clots in very rare circumstances, in addition to identifying a possible treatment for it.

The finding comes after the European Medicines Agency (EMA) investigated 19 cases of the rare blood clots out of about 14 million AstraZeneca shots given and concluded on Thursday that the benefits from the vaccine far outweigh its possible risks, although a definitive link could not be ruled out.

The EMA said there was no increased risk from blood clots and that because the AstraZeneca-Oxford vaccine is effective in preventing COVID – , which itself causes blood clots, the shot could actually reduce the risk of them overall.

But not all blood clots are the same, and 12 of the cases in Europe were of an extremely rare type called cerebral venous sinus thrombosis (CVST) – where veins that drain blood from the brain are obstructed and can potentially cause fatal bleeding.

Most of the incidents occurred within days) sh ot, and the majority were in women under the age of 35. It’s worth noting that this type of blood clot is much more common in women

, particularly during and after pregnancy and while on birth control.

WATCH | Tam says benefits of AstraZeneca vaccine outweigh risks:

Canada’s Chief Public Health Officer Dr. Theresa Tam says the benefits of the AstraZeneca COVID – 19 vaccine outweigh the rare risks. 1: 55 539

Three of the seven patients in Germany who were recently vaccinated with the AstraZeneca-Oxford shot that had this rare brain blood clot have died.

In its investigative document

, the EMA said it would expect to see just 1. 19 cases of CVST in the time period it looked at – but instead its researchers saw S.T ity ()) Germany and Italy resumed vaccinations with the shot on Friday, but France opted to vaccinate only those over with the AstraZeneca vaccine after discovering three cases of CVST. Denmark, Sweden and Norway

decided to hold off on using the vaccine until at least next week, citing the need for more time to investigate.

Findings ‘need to be investigated’

“You can not brush adverse effects under the “They always need to be investigated, and I think we have to look at this in a careful and critical manner,” said Dr. Isaac Bogoch, an infectious diseases physician and member of Ontario’s COVID – vaccine task force.

“We do not have all the information yet and we’ll learn more about this – and I imagine we’ll see some updated guidance on who should get this vaccine and perhaps who should not be getting this vaccine. “

Health Canada released a statement on Thursday saying the benefits of the AstraZeneca-Oxford vaccine outweighed the risks and that the vaccine does not increase the “overall risk of blood clots,” but it provided no update on Friday when pressed for more comment on the evolving situation.

” As the vaccine rollout continues in Canada, Health Canada will continue to monitor the use of all COVID – vaccines closely, “the statement read.

“Health Canada will examine and assess any new safety concern s, and should a safety signal be confirmed, the department will take appropriate action. “

Researchers in Norway reported identifying the mechanism early Friday, saying it was due to a” “powerful immune response ” from the vaccine.

The AstraZeneca vaccine is prepared at the local vaccination center in Hagen, Germany. Germany and Italy resumed vaccinations with the shot on Friday, the day after the European Medicines Agency found there was no increased risk of blood clots from the vaccine. (Kai Pfaffenbach / Reuters)

German researchers corroborated that finding, adding they had found a typical intravenous immunoglobulin

treatment

that can be offered to patients in hospitals if this rare type of blood clot occurs, but they said it would not work as a preventive measure.

“Of course you can not completely undo a complication,” Dr. Andreas Greinacher, a professor of transfusion medicine at the Greifswald University Clinic, said during a news conference in Germany.

“But at least now we can offer the right treatment to be able to help as quickly as possible and as efficiently as possible. “

Potential blood clot link could alter rollout in Canada

The potential link could have massive implications on the rollout of the vaccine in Canada and other countries, after use of the shot was halted in parts of Europe over safety concerns in connection with the adverse events last week.

Health officials now face the unenviable task of either adjusting the rollout or trying to restore confidence in the shot, at a time when a variant-driven third wave is unfolding and many vulnerable Canadians are vastly underprotected from COVID –

The National Advisory Committee on Immunization (NACI) recommended earlier this month that Canadians over not receive the shot , despite emerging evidence from around the world demonstrating its ability to prevent severe COVID – in older adults.

But that guidance changed on Tuesday 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 governments plans to allow those and older to receive it.

Experts say that while the guidelines for the vaccine could further change and it may not be recommended for certain age groups in the future, the protection against COVID – provided by the AstraZeneca-Oxford shot vastly o utweighs the risk of rare adverse events.

That being said, we still do not have all of the answers, and Canadians need to be aware of potential risks moving forward – however small they may be.

Medical experts in Canada divided over findings

Dr. Michael Hill, a professor of neuroscience at the University of Calgary’s Cumming School of Medicine, said on Friday that while finding out of Europe is interesting, he remains skeptical of the potential link.

“For now , the case prevalence is such that it could still be a coincidence, “he said. “We just do not know.”

Hill said that as new data emerges, new questions will arise until there is enough evidence to meet the criteria to either confirm or deny a causal link to the vaccine.

WATCH | WHO finds AstraZeneca vaccine safe and effective:

744

The World Organization’s advisory committee on vaccine saftey says the AstraZeneca COVID – benefits outweigh the risks and the shot saves lives. 1: 12

“The data will evolve further over time,” he said. “Meanwhile, a very large set of randomized trial data has shown no increased major adverse events with the AstraZeneca vaccine compared to placebo.”

Dr. David Fisman, an epidemiologist at the University of Toronto’s Dalla Lana School of Public Health, said German data offered a “compelling picture” that the rare blood clots were potentially linked to the vaccine in rare cases.

“I find myself in disagreement with Health Canada’s guidance on the use of AstraZeneca,” Fisman said.

“I do think that the use of this vaccine should be suspended in Canada until we have more data. At a minimum, I do not think it should be used in women aged 19 to 20 until we know more. “

Fisman said while the messaging around the AstraZeneca shot would be “challenging,” the continued use of the vaccine in the face of the issue that he believes will become “more apparent” as surveillance increases could erode trust in COVID – 20 vaccines.

“I appreciate that this is a sunk cost and is politically difficult. I appreciate that vaccines have become a political football, “he said.

” That said, I think suspension of use of will create short-term discomfort but is the right thing to do in the longer term. “

18

In a statement on Thursday, Health Canada said it ‘will continue to monitor the use of all COVID – 20 vaccines closely, ‘noting that the benefits of the AstraZeneca-Oxford vaccine outweigh the risks. (Hannibal Hanschke / Reuters)

Dr. David Juurlink, head of clinical pharmacology at Sunnybrook Health Sciences Center in Toronto, said th e rare events may signal a causal link with the vaccine but need to be put in context even if they are confirmed.

“If people are foregoing vaccination – AstraZeneca or otherwise – because of fear of some infinitesimally rare adverse effect, they run the risk of dying, “he said.

” I think it’s fair to make the claim that the countries in Europe that went against the advice of their regulator and suspended the use – that may cost some of their citizens in those countries their lives. “


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