AstraZeneca says U.S. trial data shows its COVID-19 vaccine 79% effective 

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AstraZeneca says advanced trial data from a U.S. study on its COVID vaccine shows it is 79 per cent effective.

Although AstraZeneca’s vaccine has been authorized in more than 50 countries, including Canada, it has not yet been given the green light in the U.S. The U.S. study comprised 30,000 volunteers, 20,000 of whom were given the vaccine while the rest got dummy shots. The results were announced Monday.

In a statement, AstraZeneca said its COVID-19 vaccine had a 79 per cent efficacy rate at preventing symptomatic COVID and was 100 per cent effective in stopping severe disease and hospitalization. Investigators said the vaccine was effective across all ages, including older people — which previous studies in other countries had failed to establish.

The early findings from the U.S. study are just one set of information AstraZeneca must submit to the U.S. Food and Drug Administration. An FDA advisory committee will publicly debate the evidence behind the shots before the agency decides whether to allow emergency use of the vaccine.

Although the vaccine is not approved for use in the U.S., it plans to send 1.5 million doses of the AstraZeneca-Oxford to Canada, perhaps as early as this week.

Scientists have been awaiting results of the U.S. study in hopes it will clear up some of the confusion about just how well the shots really work.

Britain first authorized the vaccine based on partial results from testing in the United Kingdom, Brazil and South Africa that suggested the shots were about 70 per cent effective. But those results were clouded by a manufacturing mistake that led some participants to get just a half dose in their first shot — an error the researchers didn’t immediately acknowledge.

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. 1:53

Then came more questions, about how well the vaccine protected older adults and how long to wait before the second dose. Some European countries including Germany, France and Belgium initially withheld the shot from older adults and only reversed their decisions after new data suggested it is offering seniors protection.

Last week, more than a dozen countries, mostly in Europe, temporarily suspended their use of the AstraZeneca shot after reports it was linked to blood clots. On Thursday, the European Medicines Agency concluded after an investigation that the vaccine did not raise the overall risk of blood clots, but could not rule out that it was connected to two very rare types of clots.

Later Thursday, Health Canada released a statement saying the benefits of the AstraZeneca-Oxford vaccine outweighed the risks.

During a media briefing a day later, Dr. Marc Berthiaume, director of the department’s Bureau of Medical Sciences, echoed those remarks but noted officials are “actively monitoring” emerging research on the AstraZeneca-Oxford vaccine and are in contact with European counterparts.

France, Germany, Italy and other countries subsequently resumed their use of the shot on Friday, with senior politicians rolling up their sleeves to show the vaccine was safe.

Experts buoyed by results

“These findings reconfirm previous results observed,” said Ann Falsey of the University of Rochester School of Medicine, who helped lead the trial. “It’s exciting to see similar efficacy results in people over 65 for the first time.”

Julian Tang, a virologist at the university of Leicester who was unconnected to the study, described it as “good news” for the AstraZeneca vaccine.

“The earlier U.K., Brazil, South Africa trials had a more variable and inconsistent design and it was thought that the U.S. FDA would never approve the use of the AZ vaccine on this basis, but now the U.S. clinical trial has confirmed the efficacy of this vaccine in their own clinical trials,” he said.

“Though seemingly possibly slightly less efficacious on paper, the AZ vaccine is much cheaper and much easier to store and transport than the Pfizer and Moderna vaccines currently in use in the U.S.”

AstraZeneca said it would continue to analyze the data in preparation for submitting it to the FDA in the coming weeks. It said the data would also soon be published in a peer-reviewed journal. 



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