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A person draws out Moderna vaccine during a COVID-19 vaccine clinic in Kingston, Ont., in January.Lars Hagberg/The Canadian Press

Health Canada has approved an updated version of Moderna Inc.’s COVID-19 vaccine that specifically targets the Omicron variant, making it the first “bivalent” COVID-19 vaccine cleared for use in this country.

The federal department has authorized the updated formulation for use as a booster shot in adults. It offers better protection against Omicron BA.1 – the initial strain of the Omicron variant of COVID-19 – than Moderna’s original vaccine, according to a study comparing the two versions. Health Canada has said the new vaccine is also effective against more recent Omicron subvariants, which have accounted for a growing number of Canada’s COVID-19 infections in recent months.

The approval marks a new stage in the pandemic – one in which edits to mRNA vaccines allow for a nearly real-time response to the virus’ shifting profile.

Everything you need to know about bivalent COVID-19 vaccines

Canada is receiving 10.5 million doses of the vaccine, known as “Spikevax Bivalent,” later this month, Minister of Health Jean-Yves Duclos said during a news conference Thursday. Asked when the average Canadian will be able to access the updated booster, Mr. Duclos said “supply is not an issue.”

“We are solidly ready for the fall vaccination campaign,” he said. “Provinces and territories will be able to start vaccinating with the new bivalent vaccines probably as early as next week.”

Over the summer, the prospect of an Omicron-targeted booster created some confusion among Canadians who were trying to decide whether to get third or fourth shots of the existing vaccines or wait for the new formulation. On Thursday, Canada’s Chief Public Health Officer, Theresa Tam, told reporters that a booster dose of any of the original vaccines is still preferable to no booster at all.

Moderna’s new formulation is known as a bivalent vaccine because it targets two coronavirus strains: the original strain that emerged in 2019 and the Omicron BA.1 variant.

“It’s essentially two vaccines in one,” Health Canada’s chief medical adviser, Supriya Sharma, said at a technical briefing Thursday. “While the vaccine was designed to more specifically target the Omicron BA.1 subvariant, we know that this vaccine also generates a good immune response against the Omicron subvariants BA.4 and BA.5 that have more recently emerged.”

The National Advisory Committee on Immunization (NACI) generally recommends that boosters be offered to Canadians six months after their last vaccine dose, or their last COVID-19 infection.

“Vaccine protection is like a phone battery. It needs to be recharged from time to time,” Mr. Duclos said on Thursday. “Recharging our protection after six months is important.”

NACI recommends that anyone 18 years or older who is eligible for a booster receive a bivalent version. The committee said in a statement on Thursday that children aged 12 to 17 who are moderately to severely immunocompromised or otherwise at “high risk of severe outcomes” from COVID-19 can be offered a bivalent vaccine “off-label.”

Dr. Sharma said the vaccine authorized on Thursday has been studied in humans and was found to be “almost identical” to the original Moderna COVID-19 vaccine in terms of safety.

On Wednesday, United States regulators authorized their first bivalent COVID-19 vaccines. The updated formulations – from both Moderna and Pfizer-BioNTech – are designed to target the BA.4 and BA.5 subvariants of Omicron, which are currently causing most cases of COVID-19 in the U.S.

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Moderna and Pfizer have not yet submitted their BA.4 and BA.5-targeted bivalent vaccines to Health Canada for approval. Health Canada is expecting a submission from Pfizer as early as next week, and from Moderna within the next two weeks, Dr. Sharma said. Pfizer-BioNTech submitted a BA.1-targeted bivalent vaccine for approval at the end of July, according to Pfizer spokesperson Christina Antoniou.

Howard Njoo, Canada’s deputy chief public health officer, added during the technical briefing that Canada is not alone in procuring a BA.1-targeted bivalent vaccine. Earlier this month Britain approved the same one as Canada.

Isaac Bogoch, an infectious diseases specialist at the University of Toronto, emphasized that while BA.1 and BA.5 are different sublineages of Omicron, they’re both still Omicron. He said the BA.1-tailored vaccine is “a lot closer” to the strains of the virus that are currently circulating than vaccines designed for the original strain of COVID-19.

The newly approved vaccine, he added, is “going to be an important vaccine as we move through the fall, and as we will see an expected rise in COVID cases at some point in the fall and in the winter.”

Dr. Bogoch noted that a recent study from Portugal showed that people who had BA.1 or BA.2 infections had meaningful protection against BA.5 – though he added that vaccine immunity and immunity from infections are not identical.

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