Despite controversies abroad, Health Canada says AstraZeneca vaccine is safe for use here

OTTAWA—Health Canada says the AstraZeneca vaccine has gotten bad press but remains safe for all Canadians over 18 to take.

Federal regulators are weighing whether to add an asterisk to Health Canada’s approval of the AstraZeneca vaccine for a very small minority of people who have a certain kind of rare blood clotting disorder involving low platelet counts.

But Health Canada believes there’s no reason to change its advice that overall the vaccine is safe and effective in preventing infection, severe COVID-19 disease and death.

Dr. Supriya Sharma, chief medical adviser for the federal regulatory agency, said Tuesday that public confidence might be shaken by ongoing press reports about AstraZeneca shots, but said there hasn’t been any data that causes Health Canada any real worry.

And she downplayed a question that arose in the U.S. Monday when the U.S. National Institute of Allergy and Infectious Diseases said the company had cited “outdated” data for reporting its vaccine’s efficacy rate.

AstraZeneca reported that following a large phase three clinical trial in the U.S. its vaccine showed a 79 per cent efficacy rate at preventing symptomatic COVID-19, and a 100 per cent efficacy at preventing hospitalization and death. Additional analysis by independent monitors said the efficacy rate was closer to between 69 and 74 per cent.

Sharma said much more information has emerged about the vaccine since the end of that trial in February, and Health Canada continues to have confidence in it.

Reywat Deonandan, a global health epidemiologist at the University of Ottawa, said in an interview that nevertheless public confidence “is definitely shaken” by the “muddled” AstraZeneca rollout.

He pointed to an early realization that participants in a clinical trial had received half doses not full doses, questions around its effectiveness for seniors, questions last week around “exceedingly rare” blood clots reported in Europe, and now American questions that suggest the company may have cherry-picked data to make it look better, when it didn’t need to. In fact, he said, clinical trials, even if they count tens of thousands of participants, are not big enough to pick up “extremely rare adverse events” — the one in a million case — and so no company should claim 100 per cent efficacy.

“It’s a bit of a mess-up by AstraZeneca,” said Deonandan. “It means we are losing trust in the manufacturer, unfortunately, when this vaccine looks pretty good otherwise, in my opinion. It’s shown remarkable effects in places like England and India.”

The vaccine’s troubles arise as Dr. Theresa Tam, the chief public health officer, warned Canada’s COVID-19 infections are back on the increase, a sobering reminder of “how tight the vaccines versus variants race continues to be.”

Over the past week, Canada has seen a 15-per-cent increase in cases, with a seven-day average of about 3,600 new COVID cases diagnosed daily. On Monday alone, 3,781 cases were reported.

And although deaths and hospitalizations had declined, those indicators have now levelled off or begun to tick upward slightly, as the variants of concern gain a toehold.

Canada is reporting more than 5,100 cases of the U.K. variant known as B1.1.7; 244 cases of the variant first detected in South Africa, and 124 cases of the variant first seen in Brazil.

So far only 3.5 million Canadians, of the 31 million Canadians over 16 who are eligible for shots, have received at least one dose of an approved COVID-19 vaccine. Just 637,135 Canadians are fully vaccinated against COVID-19, having received both required doses.

Tam and her deputy, Dr. Howard Njoo, urged provinces to move with caution before relaxing public health measures too quickly.

And she urged Canadians, including younger people, to mobilize whatever resources they can to help others get vaccinated, especially elderly and at-risk populations.

Sharma acknowledged confidence in vaccines is crucial, adding the most effective vaccine “only works if people trust it and agree to receive it…It’s like any other reputation, once potentially there’s some doubt that creeps into that reputation, it’s that much more difficult to gain that back.”

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She said Canada views the AstraZeneca vaccine as “an appropriate choice” for most people over 18 who are not allergic to its components. But the regulator may nonetheless add information to the AstraZeneca label in the coming days, to flag possible new information around “this type of rare clots.”

Sharma said if people experience “any of the symptoms” associated with clots in the brain, for example “if they had a sudden headache, if they have a headache that persists past three days,” they should be seen by a physician. “If they have any other symptoms of clots or shortness of breath, pain or tenderness in their calves or legs or anything like that, then they should go and be seen. Overall, we’re not making any changes to the recommendations at this point in time.”

Thrombosis Canada last week said the vaccine may be associated with “extremely rare cases of blood clots that occur in the brain (called cerebral sinus vein thrombosis) and are associated with low blood platelets,” but it should not be a concern for the general population who would benefit from a vaccine.

“These blood clots were found to occur in one in 250,000 to one in 500,000 people who received the vaccine,” said the organization. “By comparison, people who have COVID-19 are at much higher risk of developing blood clots, which occur in about one in 20 people who are in hospital with COVID-19 and in about one in 100 people who have COVID-19 but are not in hospital.”

Dr. Menaka Pai, a hematologist and thrombosis medicine physician at Hamilton Health Sciences and a professor at McMaster University, posted a series of tweets on the AstraZeneca controversy. She advised Canadians to understand that the risk of serious blood clots is “ultra rare.” She said surveillance scientists have examined data on more than 20 million AstraZeneca doses administered to date, and she trusted the regulators in Canada to keep a close eye on the data.

In the end, she said, COVID-19 is “a disease that poses a much greater risk.”

“So that ultra rare risk is outweighed by the real and common risks of COVID-19… an illness that itself gives you a greater than one in 100 risk of blood clots,” Pai said. “The biggest driver of blood clots in the COVID-19 landscape is not vaccine — it’s virus.”

AstraZeneca is the third vaccine to be approved by Health Canada after Pfizer and Moderna, two mRNA vaccines. All three require a two-dose regimen.

The fourth approved vaccine is Johnson & Johnson’s single-shot vaccine, but that vaccine has still not been delivered to Canada.

Sharma added that Health Canada does not expect to get complete clinical and manufacturing data from Novavax — a fifth vaccine under consideration for authorization — until later in April.

“It would really depend on getting both those packages of information before we were able to say how close we might be to making final decision” on Novavax — the only vaccine that has agreed to make its vaccine in Canada once a new Montreal facility is completed.