TORONTO -- Health Canada has approved the Oxford-AstraZeneca COVID-19 vaccine and a related shot by the Serum Institute of India for use in this country with the first doses expected to arrive soon.

Canada joins more than a dozen other countries that have given the green light to ChAdOx1 nCoV-19, the shot from AstraZeneca and Oxford University, which was among the first buzzed-about vaccine candidates in 2020.

A version of the AstraZeneca vaccine by the Indian pharmaceutical company Serum Institute of India and sponsored by Verity Pharmaceuticals Inc. in Canada has also been approved for use and is considered a separate vaccine by Health Canada.

The two-dose vaccines have been approved for use in people 18 years of age and older, including seniors, with the recommendation that the second dose be administered between four and 12 weeks after the first, officials said Friday.

“This is very encouraging news. It means more people vaccinated and sooner,” said Prime Minister Justin Trudeau at a press conference on Friday.

“We’re ready to get doses rolling... With Pfizer, Moderna and now AstraZeneca, Canada will get to more than 6.5 million doses by the end of March.”​

Shipments of the newly approved vaccines will amount to about 24 million doses between April and September. AstraZeneca has promised to ship 20 million doses to Canada from the U.S., with the federal government saying it’s been in talks with AstraZeneca about locking in shipments as soon as the regulatory green light was given. A timeline for the U.S. shipments has not been provided.

Another two million doses will come from the Serum Institute of India, with the first 500,000 expected by the end of March.

As well, officials anticipate 1.9 million doses as part of the global vaccine-sharing program known as COVAX. Advocates for poorer countries have criticized this shipment, saying Canada has procured enough doses through private deals. An initial COVAX batch of 500,000 doses is set to arrive in Canada from South Korea before April.

The inoculants, which are the third and fourth approved COVID-19 vaccines in Canada, is considered to be relatively cheap and easy-to-store, a factor that sets it apart from the Pfizer-BioNTech and Moderna vaccines already in circulation. AstraZeneca has reached agreements with international health bodies and governments to price each dose at about US$2.50. Doses of the AstraZeneca shot can be stored at temperatures between 2 C to 8 C, while the other two require ultra-cold freezers.

“The big, big thing that makes this different than other vaccines, which is a huge, huge advantage, is that it can be stored at refrigeration temperature,” Dr. Zain Chagla, an infectious disease specialist and associate professor at McMaster University, told CTV News Channel on Friday. 

“For a vaccine rollout to go to remote areas, to go to homeless shelters, to go to places that can’t tolerate even a -20 C fridge, this is going to be an incredible tool.”

The newly approved vaccines are the first “viral vector-based vaccines” for COVID-19 to be approved in Canada. This type of vaccine, which uses a modified cold virus commonly found in chimpanzees, has been in use for decades, said Health Canada's chief medical adviser, Dr. Supriya Sharma, on Friday.

Viral vector vaccines use a “harmless modified version of a different virus -- the vector -- to deliver instructions to our cells,” she said. “The cells begin to mark proteins from the virus that causes COVID-19, which then prompts the body to develop an immune response.”

The Pfizer and Moderna shots are both messenger RNA technology, which provide a kind of “instruction booklet” for cells to make antigens.

EFFICACY CONCERNS

The AstraZeneca vaccine has already faced efficacy concerns as variants of the novel coronavirus pop up around the world. In South Africa, officials suspended plans to use the shot on health-care workers after a clinical trial indicated it is less effective against the B.1.351 variant predominant in that country.

In France, the vaccine is only being administered to people under the age of 65, as officials cited a lack of data about its efficacy for older people. While Health Canada acknowledged Friday that the clinical trial data was limited for seniors, officials said blood tests showed people over 65 still produced COVID-19 antibodies after vaccination. Plus, the “real world evidence and post-market experience” in countries that have been using the AstraZeneca vaccine showed “a potential benefit and no safety concerns” in seniors.

CTV News Infectious Disease Specialist Dr. Abdu Sharkawy said people concerned about the efficacy of the AstraZeneca vaccines should look to a regular flu season for some “perspective.”

“A great match between a circulating flu strain and the vaccine in a given year might not exceed 60 per cent. If the flu vaccine is delivered widely in the community, we see dramatic reduction in every bad outcome,” he told CTV News Channel on Friday.

“This [AstraZeneca trial] was a multinational trial in five countries and there wasn't a single death or a single episode of really severe disease really attributable to the vaccine, [which] did a great job in reducing both of those very important metrics. 

While federal health regulators received the application for authorization from Verity and Serum Institute on Jan. 23, they were reviewing the AstraZeneca vaccine for nearly five months in collaboration with the European Medicines Agency. In early February, health officials said they were going back and forth with AstraZeneca about what information the vaccine label will include and cited ongoing trials in the U.S. as one of the reasons the review process for the jab had been “complicated.”

With files from The Canadian Press and CTV's Rachel Aiello