Do we know how effective vaccines are against the variants? Your COVID-19 questions answered

The good news is the coronavirus that causes COVID-19 doesn't seem to mutate as much or as quickly as the influenza virus that causes the flu. Drugmakers are already re-working their vaccines.

Also, will full clinical trials be needed to approve booster shots?

A health-care professional prepares a dose of the Pfizer-BioNTech COVID-19 vaccine for high-risk workers in Melbourne, Australia. (Sandra Sanders/Reuters file photo)

We're answering your questions about the pandemic. Send yours to, and we'll answer as many as we can. We publish a selection of answers online and also put some questions to the experts during The National and on CBC News Network. So far, we've received more than 71,000 emails from all corners of the country. 

Are the vaccines effective against the variants of concern?

Pfizer-BioNTech and Moderna say their COVID-19 vaccines appear to be effective against two variants of concern first identified in the U.K. and South Africa, based on blood samples from people who have been vaccinated. But more research is needed on both vaccines.

Other vaccines already have some real-world data on their effectiveness against the variants. 

Recent evidence from the United Kingdom shows that the B117 variant is a more contagious strain which causes more severe illness in the elderly and in younger age groups, said Dr. Theresa Tam, Canada's chief public health officer.

"As the number of new variant cases continue to increase, they account for a greater proportion of COVID-19 cases across Canada, reminding us of how tight the vaccines versus variants race continues to be," Tam said. 

The good news is the coronavirus that causes COVID-19 doesn't seem to mutate as much or as quickly as the influenza virus that causes the flu.

Drugmakers are already re-working their vaccines to account for variants of concern.

Phil Dormitzer, one of Pfizer's top viral vaccine scientists, said in February that his company has already made a template for a prototype vaccine targeting the variant first identified in South Africa.

(CBC News)

Dr. Supriya Sharma, Health Canada's chief medical adviser, said both laboratory tests and real-world evidence show the AstraZeneca-Oxford vaccine seems to be "quite effective" against the B117 variant first identified in the United Kingdom.

But the re-tooling plans took on new urgency after South Africa paused its rollout of the AstraZeneca vaccine after data from a small trial suggested the vaccine did not protect against mild to moderate illness from the B1351 variant now dominant in the country.

The lab research, which has not yet been peer-reviewed, involved taking blood from people who've been vaccinated to see how it performs in antibody tests against that B1351.

Sharma said that's not the only immune response and more information is needed. 

"Where it matters the most, against severe disease, hospitalization and death, it seems to be quite effective against the variant," Sharma said.

The clinical trials of both Moderna and Pfizer-BioNTech were completed before the variants of concern took off worldwide.

Dr. Noni MacDonald, a pediatrics professor at Dalhousie University in Halifax and a vaccine safety researcher, said as experts gain a more detailed and sophisticated perspective on how the COVID-19 vaccines work, they'll also gain a better understanding of what types of protection they offer.

Do we know how effective other vaccines are against B1351?

Yes, we do have some information about the other vaccines.

So far, three drugmakers — Johnson & Johnson, AstraZeneca-Oxford and Novavax — have data comparing how well their vaccines work against the B1351 variant first identified in South Africa.

The variant has a mutation that changes the shape of the viral spike protein.

As a result, lab experiments suggest the antibodies that our body produces have a harder time attaching to the spike protein, reducing the effectiveness of the vaccines, virologists say.

But infectious disease experts say the vaccines could still save lives amid B1351 cases by preventing admissions to intensive care from serious COVID-19, which reduces strain on our health-care systems — the goal of flattening the curve.

Experts with the World Health Organization said in their March 23 report that results for Novavax and Johnson & Johnson against B1351 are pending.

Preliminary data from Johnson & Johnson's subsidiary, Janssen, suggested a single-dose was 72 per cent effective against moderate to severe COVID-19 in the U.S. compared with 57 per cent effective in South Africa, where a more contagious variant was circulating at the time of the research.

WATCH | Re-tooling vaccines to keep up with coronavirus variants:

How vaccines can keep up with coronavirus variants

1 year ago
Duration 2:02
New coronavirus variants won’t necessarily mean new vaccines or vaccine boosters are needed. And if adjustments are needed, they would take less time to develop than the original vaccines.

The Novavax vaccine also showed some protection against the B1351 variant, said Dr. Isaac Bogoch, an infectious diseases physician with Toronto's University Health Network. 

In a news release, Novavax said the efficacy of its vaccine in studies from the U.K. was 89 per cent compared to 60 per cent in South Africa. 

Protection can refer to not getting the infection as well as protection against severe infection, hospitalization and death.

"So, while it isn't perfect, while it isn't the same, Johnson & Johnson, Novavax and very likely Pfizer and Moderna still provide some element of protection against that variant of concern," said Bogoch, who is also a member of Ontario's COVID-19 vaccine distribution task force.

We're hearing the variant first identified in the U.K. can be more deadly. Is this across all age groups?

"Based on the limited evidence we have, it does seem to be across all age groups," Maria Sundaram, an infectious diseases epidemiologist based in Toronto, told CBC News Network.

In January, British Prime Minister Boris Johnson said two studies presented to his government suggested the B117 variant "may be associated with a higher degree of mortality."

Patrick Vallance, Johnson's chief scientific adviser, said the previous average death rate of 60-year-olds in the U.K. from COVID-19 was about 10 per 1,000. With the new variant, roughly 13 or 14 per 1,000 infected people might be expected to die.

The relative increase in the case fatality rate "appears to be apparent across age groups," the researchers wrote. "The absolute risk of death per infection remains low."

Do you anticipate we'll need booster shots to protect against variants even after we've received both doses of a vaccine?

The answer is yes, said Bogoch.

For the first-generation of COVID-19 vaccines, Bogoch said he expects people will eventually need a booster dose.

"Down the line, and I am not sure how much farther down the line, we'd likely need a booster dose with a vaccine or an updated vaccine that accounts for the new variants of concern that are emerging," he said.

A health-care worker is seen at a COVID-19 testing centre at Ridge Meadows Hospital in Maple Ridge, B.C., earlier this month after a case of a coronavirus variant was detected at a nearby secondary school. (Ben Nelms/CBC)

MacDonald said major regulators such as Health Canada, the U.S. Food and Drug Administration and their counterparts in the U.K. and Europe are meeting virtually to discuss how to evaluate the effectiveness of vaccines against variants.

She said the regulators may ask drugmakers for what are called non-inferiority studies.

Unlike clinical trials to evaluate the efficacy of a vaccine that involve 40,000 to 50,000 people, MacDonald said non-inferiority trials need 400 to 500 people and can be done relatively quickly.

"We'll do non-inferiority," MacDonald said. "That is a simpler, easier process and it's just saying, 'Are you good if not better than what you had before?'"

Alyson Kelvin, a virologist working on COVID-19 vaccine candidates at VIDO-InterVac in Saskatoon, said surveillance in Canada and around the world will be important to see what variants people are commonly being infected with, both in vaccinated and unvaccinated populations.

"I am optimistic that we'll still have effective vaccines and we won't get into as frequently a cycle of vaccination and changing the vaccine formulations as we do with influenza," Kelvin said.

A lab technician works on blood samples taken from people taking part in a Johnson & Johnson COVID-19 vaccine study in Groblersdal, South Africa, northeast of Johannesburg, on Feb. 11. The five different vaccines submitted to Health Canada for approval may each play a role in controlling the variants. (Jerome Delay/Associated Press)

When someone is infected with the original version of the virus and they develop antibodies, those antibodies have been shown to be less effective against some new variants of concern with altered spike proteins.

Researchers have documented cases of reinfection with the variant first identified in Manaus, Brazil. But reinfections are difficult to prove since doctors need genetic proof showing a distinct coronavirus variant caused each instance of infection. 

Our bodies generate antibodies to fight off a natural infection. Besides antibody-based immunity, our immune system also has T-cell immunity, or cell-based immunity. T cells are a type of white blood cell. 

Kelvin said cell-based immunity is often broader than what we get from just antibodies.

Immunologists say antibodies are also relatively short-lived compared with some T cells

Kelvin said it will be important for researchers to watch for any breakthrough infections from a variant that suggest both arms of immunity are no longer effective.

Alyson Kelvin, who is working on different coronavirus vaccine candidates, is seen in her lab at VIDO-InterVac in Saskatoon, last March. She says she's optimistic we will still have effective vaccines against the variants. (Liam Richards/The Canadian Press)

Brian Lichty of the McMaster Immunology Research Centre in Hamilton, who is also working on COVID-19 vaccine candidates, said genes for the variants can be swapped into an existing mRNA vaccine, such as those made by Pfizer-BioNTech and Moderna.

"Technically, it's really simple," Lichty said. "I can, with my laptop, design a new vaccine in 20 minutes sitting on my couch."

Then, in the lab, the new gene is synthesized. Finally, the new vaccine is mass manufactured — the step that takes the most time, he said.

Looking ahead, drugmaker GlaxoSmithKline (GSK) said it will work with the German pharmaceutical company Curevac to develop an mRNA vaccine against the variants.

The advantage of existing mRNA vaccines from Pfizer-BioNtech and Moderna compared with vaccines based on older technologies is they don't need cells or tissue culture to grow. That's one reason why it is easier to change recipes in their manufacturing lines to address the variants, MacDonald said.

With files from CBC's Christine Birak and Associated Press


To encourage thoughtful and respectful conversations, first and last names will appear with each submission to CBC/Radio-Canada's online communities (except in children and youth-oriented communities). Pseudonyms will no longer be permitted.

By submitting a comment, you accept that CBC has the right to reproduce and publish that comment in whole or in part, in any manner CBC chooses. Please note that CBC does not endorse the opinions expressed in comments. Comments on this story are moderated according to our Submission Guidelines. Comments are welcome while open. We reserve the right to close comments at any time.

Become a CBC Member

Join the conversation  Create account

Already have an account?