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A man receives his COVID-19 vaccine at a clinic at Olympic Stadium in Montreal on March 1, 2021.Paul Chiasson/The Canadian Press

Canadians tempted to shop for a preferred COVID-19 vaccine have been given simple advice from experts who have examined the country’s three available options: Take what is offered as quickly as possible.

The vaccine study and approval processes have swamped the public with numbers about vaccine efficacy, how long immunity may last, details about the difference between innovative and traditional vaccine platforms and shifting schedules for administering doses.

The bottom line for Canadians who are accustomed to using consumer skills to find the best option is simple, according to Tania Watts, an immunologist at the University of Toronto: “I would take what is offered as it decreases your likelihood of severe disease and death.”

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Moderna, Pfizer, AstraZeneca or Johnson & Johnson: Which COVID-19 vaccine will I get in Canada?

Canada pre-purchased millions of doses of seven different vaccine types, and Health Canada has approved four so far for the various provincial and territorial rollouts. All the drugs are fully effective in preventing serious illness and death, though some may do more than others to stop any symptomatic illness at all (which is where the efficacy rates cited below come in).

PFIZER-BIONTECH

  • Also known as: Comirnaty
  • Approved on: Dec. 9, 2020
  • Efficacy rate: 95 per cent with both doses in patients 16 and older, and 100 per cent in 12- to 15-year-olds
  • Traits: Must be stored at -70 C, requiring specialized ultracold freezers. It is a new type of mRNA-based vaccine that gives the body a sample of the virus’s DNA to teach immune systems how to fight it. Health Canada has authorized it for use in people as young as 12.

MODERNA

  • Also known as: SpikeVax
  • Approved on: Dec. 23, 2020
  • Efficacy rate: 94 per cent with both doses in patients 18 and older, and 100 per cent in 12- to 17-year-olds
  • Traits: Like Pfizer’s vaccine, this one is mRNA-based, but it can be stored at -20 C. It’s approved for use in Canada for ages 12 and up.

OXFORD-ASTRAZENECA

  • Also known as: Vaxzevria
  • Approved on: Feb. 26, 2021
  • Efficacy rate: 62 per cent two weeks after the second dose
  • Traits: This comes in two versions approved for Canadian use, the kind made in Europe and the same drug made by a different process in India (where it is called Covishield). The National Advisory Committee on Immunization’s latest guidance is that its okay for people 30 and older to get it if they can’t or don’t want to wait for an mRNA vaccine, but to guard against the risk of a rare blood-clotting disorder, all provinces have stopped giving first doses of AstraZeneca.

JOHNSON & JOHNSON

  • Also known as: Janssen
  • Approved on: March 5, 2021
  • Efficacy rate: 66 per cent two weeks after the single dose
  • Traits: Unlike the other vaccines, this one comes in a single injection. NACI says it should be offered to Canadians 30 and older, but Health Canada paused distribution of the drug for now as it investigates inspection concerns at a Maryland facility where the active ingredient was made.

How many vaccine doses do I get?

All vaccines except Johnson & Johnson’s require two doses, though even for double-dose drugs, research suggests the first shots may give fairly strong protection. This has led health agencies to focus on getting first shots to as many people as possible, then delaying boosters by up to four months. To see how many doses your province or territory has administered so far, check our vaccine tracker for the latest numbers.

COVID-19 news: Updates and essential resources about the pandemic

While no direct head-to-head study has been conducted on the COVID-19 vaccines, current data suggest the AstraZeneca shot is just as effective as the Moderna and Pfizer-BioNTech mRNA vaccines at preventing serious illness and death. However, it may be less effective at preventing mild illness.

This difference was enough for an independent committee of experts to draw a distinction between AstraZeneca’s vaccine and the two others in recommendations that were published online Monday by the Public Health Agency of Canada.

The committee determined there were not enough data to recommend the AstraZeneca vaccine for Canadians who are 65 and older, a position also taken by some European countries.

The new recommendations also make clear that those who have previously been prioritized for vaccination, including front-line workers and Indigenous Canadians, should receive the mRNA vaccines as a first choice. In cases where an mRNA vaccine is not available, AstraZeneca should be given when “the advantages of earlier vaccination outweigh the limitations of vaccinating with a less efficacious vaccine” and when the recipient provides informed consent after a discussion about “current local vaccine options.”

When asked if the committee’s more restrictive recommendations for the AstraZeneca vaccine might prompt some people to hold off from taking it when offered, vice-chair Shelley Deeks said, “Vaccine acceptance is one consideration for the committee. ... However we also need to ensure that we examine the available data and make evidence-based recommendations.”

Dr. Deeks, a physician and the surveillance medical officer of health for Nova Scotia, added the committee would continue to revise its recommendations as data become available and more vaccines are authorized. This could occur in a matter of days if the Johnson & Johnson single-dose vaccine is approved by Canadian regulators.

The Public Health Agency of Canada responded to the recommendation with a statement saying “the best vaccine for a Canadian is the one they can get.” The agency noted the AstraZeneca shot showed no safety concerns in clinical trials or among seniors already vaccinated in other countries, and is showing some benefits in older populations including reduced chance of hospitalization.

Last month, University of Edinburgh researchers reported that the vaccination of more than 1.1 million individuals in Scotland with the AstraZeneca and Pfizer-BioNTech vaccines had reduced the risk of hospitalization because of COVID-19 by up to 94 per cent and 85 per cent, respectively.

British Columbia announced Monday it will start a second-track vaccination campaign for essential workers using the refrigerator-stable vaccines such as the AstraZeneca shot. Older and vulnerable populations will continue to receive the Moderna and Pfizer vaccines, which require deep freezing and more preparation.

Bonnie Henry, B.C.’s Provincial Health Officer, said essential workers will have the option to continue waiting their turn for mRNA vaccines if they do not want the AstraZeneca dose.

“There will be a little bit of choice but not a whole lot,” Dr. Henry said. “We encourage people to get the vaccine available to them.”

In Quebec, Daniel Paré, the head of the province’s vaccination program, said Monday that people will not get to choose which vaccine they get, although they will be informed of which dose is coming before they get the needle.

“With a global shortage of vaccine, we use the vaccine that is safe and effective and available,” Mr. Paré told Montreal radio 98.5.

Dr. Watts at the University of Toronto said concentrating the mRNA vaccines on older and immunocompromised people may make sense because those vaccines have higher efficacy than AstraZeneca’s. People in those categories also have a weaker immune response, she said.

All three vaccines share some unknown factors, such as how long immunity lasts, how long the booster shot can wait and whether they can be used interchangeably in second doses, she said.

Jennifer Gommerman, also an immunologist at the University of Toronto, agreed mRNA vaccines “may be a better choice for groups with less immune response.”

“But for the rest of us, in the name of herd immunity, I would take what’s given as it contributes to the war on COVID,” she said. “All the vaccines prevent severe COVID requiring hospitalization. If you are offered a vaccine, you take it.”

The initial COVID-19 vaccinations in Canada and around the world raise questions about how people react to the shot, how pregnant women should approach it and how far away herd immunity may be. Globe health reporter Kelly Grant and science reporter Ivan Semeniuk discuss the answers.

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