The approval by Health Canada follows that of Pfizer and Moderna, both of which also require two doses.
The AstraZeneca shot is less effective in clinical trials than its rivals’ injections — 62 per cent in preventing symptomatic cases versus the high 90s — but offers distinct benefits.
One major advantage is in logistics. The shot can be stored and transported at normal refrigerated temperatures, unlike its leading mRNA-based competitors, which require ultra-cold storage.
The authorization gives Canada’s overall vaccine supply a significant boost.
AstraZeneca has agreed to provide up to 20 million doses to Canada in the second and third quarters of this year. That is on top of the 23 million combined doses expected from Pfizer-BioNTech and Moderna during the same period.
Prime Minister Justin Trudeau also announced Friday that two million additional doses of the AstraZeneca vaccine will be produced by the Serum Institute of India and shipped to Canada.
Federal officials say that 500,000 of those doses will arrive “in the coming days.” The remaining 1.5 million doses will begin to arrive in Canada over the next few months.
On top of that, Canada expects to receive 1.9 million doses of AstraZeneca through COVAX, the global vaccine-sharing initiative, by the end of June.
While the official delivery schedule is still being confirmed, Procurement Minister Anita Anand suggested that it’s possible Canada’s goal of providing vaccines to all who want one by September could be met sooner.
“By all means, we’re moving up doses and deliveries of doses with the end in mind,” she said Friday.
Data slowed approval
Health Canada has said the vaccine has been “a bit complicated” to review.
One of the reasons is because of a mix-up in how big the doses were during the clinical trials. Some volunteers only received a half dose at first, according to Dr. Supriya Sharma, Health Canada’s chief medical adviser.
The age of the trial participants also made it difficult to finalize the rules for how the vaccine is to be used and on whom, since the first two phases of AstraZeneca’s trials did not include people over the age of 65.
Health Canada has approved the shot for all adults — anyone 18 years and older. Sharma said that while the vaccine was not tested on people over the age of 65, “emerging, promising” real-world data from countries already using the product suggest it is safe and effective among older age groups.
“For someone 65 years and older, the question is, the benefits of getting the vaccine versus not, will it outweigh the risk? The answer to that is yes, based on all the information we have,” Sharma said at a briefing Friday.
If there are other vaccines available, recommending which one is best for what population will come from the National Advisory Committee on Immunization (NACI), Sharma said. From there, it’ll be up to provinces and territories to decide how and to whom they dole out each vaccine.
But we’re not quite there yet, Sharma said.
“Having this vaccine on top of the others will help to increase population immunity,” she said.
There are two doses to the vaccine. The second can be given between four and 12 weeks after the first.
“Evidence suggests the efficacy increases with longer dosing intervals… that’s what was reflected in the clinical trials,” Sharma said.
“Within that range, there are some trends in the data that show closer to the 12 weeks you can actually see a better immune response, so more effectiveness, more efficacy. The issue with the trials is that the numbers are not sufficient to recommend only that timeline.”
As with other vaccines, common side effects include tenderness at the injection site, headache and fever. The vast majority of adverse reactions in trials were “mild to moderate” in severity, Sharma said, and were resolved “within a few days.”
Studies point to benefits
More recent studies suggest the shot could offer a number of significant benefits. Preliminary findings from Oxford University, co-developer of the vaccine, hint that it may also reduce transmission of the virus and offers strong protection for three months on just a single dose.
So far, makers of all vaccines have said that their shots proved to be highly effective in protecting people from illness caused by the virus, but it was unclear whether the drugs could also suppress transmission of the virus.
It may also be a strong contender in the protection against COVID-19 variants, particularly the B.1.1.7 variant.
The companies have said that their vaccine has similar efficacy against the variant, which first began circulating in the U.K. but has since made a mark on Canada, particularly in Ontario and Alberta.
However, preliminary data suggests the vaccine offers only “minimal protection against mild or moderate disease” from the B.1.351 variant. This variant was first found in South Africa and is now the dominant form of the coronavirus in that country. The findings caused the country to halt the use of the product earlier this month.
The study, which has not yet been peer-reviewed, has drawn skepticism from Canadian experts, who say it’s premature to come to any conclusions.
Oxford University, co-developer of the vaccine, has said its researchers were in the process of tweaking the product to better protect against the variant.
AstraZeneca’s vaccine is also mired in some political controversy.
A bitter dispute between the drugmaker and the European Union has stirred threats of export controls that could block shipments to non-EU countries, like Canada.
Recently, the company has become embroiled in supply issues with the EU. It was initially reported the drugmaker would not be able to fulfil its second-quarter supply commitment to the EU due to production issues. However, the company later backtracked and insists the promise will be kept.
Canada is set to get the bulk of its vaccines from the U.S., but potentially factories in Europe, too.
Trudeau has maintained that the possible measures from the EU would not hamper Canada’s agreements on deliveries. The threat has so far not impacted deliveries from Canada’s other approved vaccines, such as Moderna.
As for the U.S., Trudeau said Friday that “all indications” so far are that the vaccines will get to Canada without issue.
The AstraZeneca vaccine has already been approved in the EU as well as in several countries, including the U.K. The World Health Organization also gave the shot its approval this month, allowing vaccinations to begin in developing countries.
From a global standpoint, its low cost is also a major advantage. It runs about US$4 ($5) per dose.
AstraZeneca, which says it aims to manufacture up to three billion doses in 2021, has pledged to make its product available at cost around the world until at least July.
— with files from Reuters and the Canadian Press