A look at bivalent COVID-19 vaccines as the fall surge looms


A jar filled with empty vials of COVID-19 vaccine is displayed at Junction Chemist Pharmacy during the COVID-19 pandemic in Toronto on April 6, 2022.Nathan Denette/The Canadian Press

Canada is increasingly expected to approve an updated version of the COVID-19 vaccine as the fall threatens to trigger a new wave of infections.

Earlier this week, UK regulators became the first in the world to authorize Moderna’s bivalent vaccine, which protects against both the original strain of the novel coronavirus and the Omicron BA.1 subvariant.

Health Canada is currently reviewing bivalent booster candidates from Moderna and Pfizer-BioNTech, leaving some Canadians wondering whether to wait for the revamped shots or opt for a booster now.

With viral circulation expected to increase as the season changes, some provinces are encouraging people to get a booster of the approved version of the vaccine. For many people, that would mean a fourth or fifth dose of the original formula.

Experts say the extent to which bivalent vaccines provide additional protection against catching COVID-19 is still being studied, and the cost-benefit analysis of waiting for a vaccine depends on the person.

Here’s a look at what we know about bivalent vaccines and how they might factor into a crash wave.

When will bivalent vaccines be available?

Health Canada received Moderna’s bivalent vaccine application on June 30, while its British counterpart obtained the necessary documents to begin its review earlier that month, spokesperson Mark Johnson said in an email. Pfizer filed a submission for its updated snapshot on July 25.

Although the agency did not provide a timeline for the completion of these reviews, Health Canada has already asked vaccine makers to further tweak their bivalent vaccines to target the spreading Omicron BA.4 and BA.5 subvariants. fast “as soon as possible,” Johnson said.

Canada’s chief public health officer, Dr Theresa Tam, says Canada has secured a “sufficient” supply of bivalent vaccines if regulators give the go-ahead for a rollout.

Infectious disease specialist Dr. Zain Chagla said he expects to see more countries allow bivalent vaccines in the coming weeks and months, which should give Canada time to integrate vaccines updated in its fall vaccination campaign.

How do bivalent boosters compare to original vaccines?

Currently available COVID-19 vaccines are monovalent – ​​suitable only for the original novel coronavirus. In addition to defending against this earlier strain, the proposed bivalent vaccines have been designed to recognize specific mutations in Omicron’s spike protein that make it more effective at evading immune detection.

These updated vaccines may provide additional “gradual” protection against Omicron uptake, but the extent remains to be seen, Tam said.

Chagla, an associate professor at McMaster University in Hamilton, said bivalent vaccines might not be the game-changer some were hoping for in curbing the spread of the virus.

While the BA.4 and BA.5 Omicron subvariants are gaining traction across much of the country, bivalent vaccines tailored to BA.1 might not be much better than a first-generation booster when it comes to light. acts to deter COVID-19 infection, Chagla said.

Emerging research suggests that the protection provided by currently available boosters diminishes within six to eight weeks, Chagla said. He expects bivalent vaccines to extend that period by a few more weeks, not months.

“I’m happy to be wrong,” he said. “But I don’t know if it will reset the clock.”

Old and new versions of COVID-19 vaccines are effective in preventing serious consequences of COVID-19, he noted.

Should I wait before receiving a bivalent vaccine?

The short answer is: it depends.

Provinces have expanded access to the fourth — and in Quebec, the fifth — doses of the original COVID-19 vaccine on the expectation that COVID-19 cases will rise as temperatures drop.

With the healthcare system already stretched to its limits, the priority must be to strengthen those most at risk of landing in hospital, such as the immunocompromised and the elderly, Chagla said.

But since more of the population has acquired hybrid immunity, it wouldn’t be unreasonable for people at low risk to wait for the latest version of the vaccine, Chagla said.

Tam encouraged Canadians to weigh both their personal risk and the level of spread of COVID-19 in their community. But if more than six months have passed since your last infection or vaccination, you might want to roll up your sleeves for another shot before the cold sets in, she said.

“If you’ve waited too long, the wave might start,” she said. “So you don’t get as much benefit from it.”

And after?

A key challenge in controlling COVID-19 is that the evolution of the virus has far exceeded the time it takes to develop, test, manufacture, review and deploy a vaccine capable of countering the latest mutation.

“By the time the wave hits – two to three months – it’s barely enough to scratch the surface of getting a new vaccine,” he said. “There’s this catch-up game that happens all the time.”

He hopes the inaugural rollout of bivalent vaccines could provide “proof of concept” that will speed up this process for future iterations of the vaccine, the same way the flu vaccine is modified each fall to target variants that are circulating.

“There’s nothing wrong with it being a flu season-like pattern, where people are just being updated for a while,” he said.

Although we cannot expect perfect protection against disease, we can have the tools to prevent serious illness in the most vulnerable.

“We are lucky to have this technology.”


Comments are closed.