Health Canada has formally approved Moderna's updated COVID-19 vaccine targeting the Omicron variant.
The vaccine, which has been approved for use in adults 18 and older, will become the first COVID-19 vaccine available in Canada that targets Omicron in addition to the original strain of the coronavirus.
In a decision summary made public Thursday, Health Canada said the new vaccine shows "significantly higher responses" to the Omicron BA.1 virus in comparison to Moderna's original coronavirus vaccine, officially branded as Spikevax.
While the updated vaccine was developed to target the Omicron BA.1 variant, Health Canada says clinical trials suggest the new vaccine still elicits a "stronger immune response" against the more recent mutations of Omicron — BA.4 and BA.5 — which are now dominant.
"Results of exploratory analyses suggest that a second booster with Spikevax Bivalent would provide a superior neutralizing antibody response against BA.4/5 compared to a second booster with Spikevax Original," reads a portion of the decision.
Health Canada also reports that "no new safety concerns have been identified in studies when compared to the currently approved Spikevax mRNA vaccine."
The National Advisory Committee on Immunization recommends that the updated vaccine be offered to adults who are recommended to receive a fall booster dose.
NACI says adolescents between 12 and 17 with "moderately to severely immunocompromising conditions" and those who have elevated social risk factors could also be offered the vaccine.
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The updated vaccine is a combination of two strains, also known as "bivalent" shots. It contains both the original vaccine formulation and protection against the original Omicron variant BA.1.
The new Moderna shot will be delivered in 50 microgram doses. Half of its contents target the original coronavirus strain while the other half target Omicron.
An initial shipment of 780,000 doses of the updated vaccine is set to arrive in Canada on Friday, Health Minister Jean-Yves Duclos said. An additional 10.5 million doses will be delivered by the end of September.
Deliveries to the provinces and territories, which oversee the administration of vaccines, are set to begin next week.
Duclos urged Canadians to sign up for booster shots quickly as summer comes to an end.
"This fall will be challenging, with the return of the flu and other respiratory diseases and people moving indoors," Duclos told a news conference on Thursday afternoon.
Vaccines for newer Omicron strains may be coming
Both Moderna and Pfizer have developed even newer bivalent vaccines targeting the Omicron BA.4 and BA.5 strains, but the companies have not yet submitted those products for approval by Health Canada.
Njoo said that in choosing to approve Moderna's BA.1-focused vaccine, the government considered the tools it has now "versus what might potentially happen in the future."
"At the end of the day, we're very comfortable with the fact that we have a good bivalent vaccine," Njoo added.
Omicron BA.5 is the dominant COVID-19 subvariant in Canada
The U.S. Food and Drug Administration announced Wednesday its approval of bivalent vaccines by Pfizer and Moderna that specifically target the more recent Omicron BA.4 and BA.5 strains.
Dr. Supriya Sharma, the chief medical adviser with Health Canada, said the agency expects to receive a submission from Pfizer as soon as next week for a bivalent vaccine targeting BA.4 and BA.5.
A new submission by Moderna for BA.4 and BA.5 is also expected within the next two weeks, Sharma said.
A spokesperson for Pfizer Canada told CBC News Wednesday that its submission to Health Canada for a BA.1-targeted bivalent vaccine is still under review and approval has not yet been granted.
WATCH: Infectious diseases physician says Canadians shouldn't wait for updated boosters:
Angela Rasmussen, a virologist with the University of Saskatchewan's Vaccine and Infectious Disease Organization, said the vaccine's approval is an important development in Canada's fight against COVID-19 — even though the shot was developed for a strain that is no longer circulating widely.
"I do think it's really important now for people to know that the BA.1 vaccine is still going to really improve immunity against the variants that are circulating," Rasmussen told CBC News.
Another expert said Canadians should not wait for the perfect and most up-to-date vaccine, since they'll likely need repeated COVID-19 immunizations in the future.
"That protection will not last. This will not be the last vaccine you get. So prepare, until we have vaccines that are better, to be vaccinated probably every six months," said Dawn Bowdish, an immunologist at McMaster University.