Moderna says vaccine appears effective against new coronavirus variants — but less so for one

The two-dose Moderna vaccine approved for use in Canada appears to protect against the coronavirus variants first identified in the U.K. and South Africa, the company announced on Monday.

Vaccine may be less effective against variant found in South Africa, company's study shows

The two-dose Moderna vaccine currently approved for use in Canada appears to protect against two key coronavirus variants, the company announced on Monday, though it may be less effective against the B1351 variant found in South Africa. (Greg Lovett /Northwest Florida Daily News/The Associated Press)

The two-dose Moderna vaccine approved for use in Canada appears to protect against the coronavirus variants first identified in the U.K. and South Africa, the company announced on Monday.

However, it may be less effective against the B1351 variant found in South Africa, according to studies conducted by the company, which is now developing an alternative version of the vaccine for booster shots.

"It's clearly good news," said Toronto-based infectious disease specialist Dr. Isaac Bogoch, a member of Ontario's vaccine distribution task force.

A booster shot being in development is not unexpected, he added, to ensure immunity against the evolving SARS-CoV-2 virus, including the B1351 variant.

"It might have some slight reduction in response, but the vaccine is still expected to work," Bogoch stressed.

Moderna exploring booster shot

Moderna's latest findings, which have not been released publicly beyond a news release, are from a study conducted in collaboration with the Vaccine Research Center at the National Institute of Allergy and Infectious Diseases, part of the U.S. National Institutes of Health.

The manuscript has been submitted as a preprint to bioRxiv and will be submitted for peer-reviewed publication, the company said.

The study showed no significant impact on the vaccine's neutralizing power against the B117 variant first identified in the U.K., relative to prior variants.

However, for the B1351 variant, there was a six-fold reduction in neutralizing ability compared to use on prior variants, though the company said the levels remain above what are "expected to be protective."

Neutralizing antibodies are among the body's immune responses to control viral infections.

"It is a little worrisome that you see a lesser neutralizing antibody response, but that doesn't necessarily mean that you are unprotected," said Dr. Paul Offit, an infectious disease expert at the University of Pennsylvania and a member of the U.S. Food and Drug Administration's vaccine advisory panel.

Offit added that even these lower levels may still be enough to protect against serious infections.

"The goal of this vaccine is to keep you out of the hospital and to keep you out of the morgue," he said. "If you get a symptomatic infection or mildly symptomatic infection that is not a burden to the health-care system."

There is also much more to the body's immune response than just antibodies, Bogoch noted.

Even so, Moderna is exploring a booster shot targeting the B1351 variant.

"Out of an abundance of caution and leveraging the flexibility of our mRNA platform, we are advancing an emerging variant booster candidate against the variant first identified in the Republic of South Africa into the clinic to determine if it will be more effective to boost titers against this and potentially future variants," Moderna CEO Stéphane Bancel said in a statement.

Vaccines will likely need updates 'periodically'

Bogoch likened that approach to how vaccine manufacturers have long tackled the ever-evolving influenza virus.

"Every year, we update our influenza vaccine to really tie in to what the circulating strain is," he said. "Maybe it's going to be every year, or every few years, but we'll likely have to update these vaccines periodically."

The greater concern for scientists right now isn't the current slate of known variants — which may be both more-transmissible and, in the case of B117, possibly more deadly — but those that could emerge in the future.

Given the widespread virus transmission and high case counts of COVID-19 in Canada and abroad, researchers say there are ample opportunities for the coronavirus to keep evolving, potentially developing variants that may one day evade current vaccines entirely.

There have been dozens of cases of variants confirmed in Canada in recent weeks despite limited surveillance, including at a Barrie, Ont., long-term care home where the B117 variant was reported in relation to a devastating outbreak that rapidly swept through the facility and has left at least 41 people dead.

"I think the take-home message here is we have to still be very careful about circulating variants because eventually we're going to find one where the vaccine will have reduced efficacy," Bogoch said.


Lauren Pelley

Senior Writer

Lauren Pelley is a Senior Writer for CBC News who covers health and medicine, including the COVID-19 pandemic. She's based in Toronto. Contact her at:

With a file from Reuters


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?