Health Canada has authorized Pfizer’s vaccine for the coronavirus. But the initial shipment won’t be ready for use by children under 16 as Pfizer continues clinical trials on the vaccine.

The vaccine has been approved under an interim order. There will be “complementary studies” that will be conducted on young people under 16, health officials say.

The Pfizer vaccine requires two doses to be taken 21 days apart. Research so far suggests the vaccine is effective for two months and possibly up to six months, according to health officials. The release of the vaccine is to begin the work of stemming the tide of infections in the general population and growing numbers being admitted to the hospital during the second wave of the virus.

Health Canada says it is also monitoring three other vaccine candidates for possible future use in Canada.

The news announced during a press conference today (December 9) comes a day after Prime Minister Justin Trudeau announced that some 249,000 doses of the vaccine would be available by year’s end. That will be the beginning of an organized rollout that Trudeau described as a “gradual process” that is not expected to hit high gear until spring 2021. Some 14 distribution sites, including two each in Ontario and Quebec, have been established for the vaccine rollout.

Health Canada, which is known for its stringent requirements when it comes to drug approvals, has been conducting what’s called a “rolling review” of the Pfizer vaccine since October. It released a number of documents related to its approval “in the interests of transparency”. The documents include what Health Canada describes as a “high-level summary of the evidence that Health Canada reviewed to support the authorization of the vaccine”.

Health Canada says a more detailed analysis of the scientific evidence and clinical trial data used to grant approval will be released “in the coming weeks”.

“Canadians can feel confident that the review process was rigorous and that we have strong monitoring systems in place,” the health agency stated.

The statement goes on to say that “Health Canada and the Public Health Agency of Canada will closely monitor the safety of the vaccine once it is on the market and will not hesitate to take action if any safety concerns are identified.”

As part of the terms and conditions of Canada’s contract with Pfizer, the manufacturer will continue providing data on “the safety, efficacy, and quality of the vaccine to ensure the benefits of the vaccine continue to be demonstrated through market use.”

The Interim Order issued by Health Canada along with its approval states that the health minister “may suspend an authorization, in whole or in part” of the vaccine “if the Minister has sufficient evidence to support the conclusion that the risks of the vaccine outweigh the benefits.”

The Pfizer vaccine, which is known as an mRNA vaccine, employs a new technology that can “teach our cells how to make a protein that will trigger an immune response”. Other vaccines use “live viruses” to inoculate people against the effects of a virus. 

Pfizer vaccine side effects “mild or moderate”

Health Canada says that the side effects observed so far in Pfizer’s COVID-19 vaccine clinical trials have been “mild or moderate”. Those include pain at the site of the injection, body chills, fatigue, and fever.

The “warnings and precautions” section of documents released by Health Canada advises those with bleeding problems, those who bruise easily or use blood thinning medication, or are pregnant or plan to become pregnant to talk to their healthcare professionals before taking the vaccine.

Health Canada says Pfizer will continue to follow clinical trial participants for at least two years. Pfizer says the vaccine “may take until 7 days after the second dose to develop protection against COVID-19”. 

Government health officials say allergic effects reported in the U.K., which began administering the Pfizer vaccine this week, should not be a major cause for concern. Those were “short-lived and resolved” and appeared among patients who reportedly had a history of reactions to other drugs. Of some 22,000 vaccinated in Pfizer’s trials, only two cases reported more serious adverse side effects, government officials say.