OTTAWA— It appears Canada’s approval of AstraZeneca’s COVID-19 vaccine is close.
Health Canada’s chief medical adviser Dr. Supriya Sharma said Monday that the regulator is in the “final stages” of reviewing the two-dose vaccine, which was developed by AstraZeneca with researchers at Oxford University, for use in Canada.
Although that’s the same thing Health Canada has said since Feb. 9, Sharma indicated it is now weighing what use Canada should recommend for the vaccine, what it should require on the vaccine label, and what should be the terms and conditions put on the company for ongoing monitoring of its vaccine.
“Currently we’re still going back and forth with the company with respect to some data. We’ve just had some conversations with them today. It is in the final stages,” Sharma told the House of Commons health committee. “But that end process around the product monograph, the labelling, the indications, the risk management plan and potential terms and conditions on the vaccine are still under discussion.”
Sharma acknowledged that approval has taking longer than it did for the Pfizer-BioNTech or Moderna vaccines, which were given the green light in December. Those are both mRNA-based vaccines, which use bits of genetic code to prompt the human body to build antibodies to the coronavirus spike protein that the virus uses to attach and enter cells.
The AstraZeneca vaccine is a viral vector vaccine, which uses a modified cold virus found in chimpanzees to stimulate an immune response to the real coronavirus. It is also easier to handle, store and transport at normal fridge temperatures than the frozen mRNA vaccines produced by Pfizer-BioNTech and Moderna. Canada has prepurchased 20 million doses of the AstraZeneca vaccine, and is eligible to receive another 1.9-million doses through the global COVAX vaccine distribution facility.
Sharma said Canada’s review is “complicated” because AstraZeneca collected its data differently than did Pfizer and Moderna. While other countries’ medical regulators have already approved the AstraZeneca vaccine, she noted they’ve approved it for different uses.
She also noted that although the European Medicines Agency has authorized use of the vaccine, the U.S. Food and Drug Administration “is still waiting.”
While the European agency that Canada is working with has approved it, European countries have set their own limits. For example, France recommends the AstraZeneca vaccine not be used for people over 65, while Switzerland has not authorized its administration at all, saying there isn’t enough data.
AstraZeneca has been approved by the World Health Organization for distribution to developing countries through the COVAX global sharing program. It’s also been approved by Argentina, Mexico and Morocco.
Last week, Australia approved AstraZeneca as a two-dose vaccine for use in people aged 18 and over, with doses spaced four to 12 weeks apart. However, Australia’s regulator also said a 12-week dosing interval is ideal to prompt the best immune response and to maximize “broader community coverage” as the vaccine is rolled out.
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Sharma underscored that Health Canada still believes a second dose of two-dose vaccines that are already approved is required because there isn’t enough data yet to allay concerns that immunity “could wane after a period of time.”
She said data collected in British Columbia and Quebec on the effectiveness of the Pfizer and Moderna vaccines is “very important” because it showed that a first dose of works well in older age groups, and that a longer delay between doses will not have a significant effect.
Sharma called that data “useful, but it is limited” and said Health Canada’s authorization still requires two doses. Vaccine producers would have to come back with more evidence to seek new approvals if they wanted to switch to a single-dose regimen, she said.
However, Dr. Alan Bernstein, head of the Canadian Institute for Advanced Research suggested that the different vaccines could be “mixed and matched.”
Bernstein, who is on Canada’s vaccine task force, said that for viral vector vaccines like the AstraZeneca-Oxford vaccine, “the second time you come in with the second shot, the host will already have perhaps mounted an immune response against the vector itself, so you’ll have a diminished effectiveness of the vaccine the second time around, whereas if you only give it once and come in with the mRNA vaccine, you’re combining the best of both worlds.”
Evidence shows that mRNA vaccines are effective at prompting a recipient to make viral antibodies, he said, while viral vectors are “particularly good at activating another arm … the cellular arm of our immune system.”
“If we find you have a lot of one and not the other, it’s another argument for doing both,” he said.
Bernstein said Canada should work with the U.K. and conduct clinical trials to do comparisons, saying those could be completed within two months.
Bernstein also gave a glimpse at Canada’s ill-fated effort to work with the Chinese company CanSino. He said the National Research Council was already collaborating with CanSino when the vaccine task force was formed last June, he said, “so when they came in front of us, it was partly an FYI, partly for us to comment on the science.”
The task force told the government there was “good news and bad news. The good news was at that point CanSino was way out in front of any vaccine developer in terms of having a vaccine for human use for COVID19,” he told the committee. “The bad news was the science.”
Bernstein said there was “a question about how effective that vaccine would be, and so we provided that information back to them. When we saw the later data, later in the summer, we recommended that the collaboration end.”
Tonda MacCharles is an Ottawa-based reporter covering federal politics for the Star. Follow her on Twitter: @tondamacc
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