CANADA Why is the timing of your next COVID shot...

Why is the timing of your next COVID shot important?


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Timing our next shots before a new potential wave or when new options start to emerge in Canada so we don’t fall into the trap of trying to roll out doses in the midst of a rapidly deteriorating wave. (Matt Rourke/Associated Press)

The timing of your next COVID-19 vaccine may be more important than ever as highly contagious sub-variants of Omicron are on the rise in Canada, and waning immunity from previous vaccination and infection threatens to spark another surge.

Canada is once again a hotbed of options, with BA.2.12.1 currently accounting for over 40 percent of COVID cases, while BA.4 and BA.5 are rapidly gaining momentum, totaling over 10 percent combined at the end of May. a significant jump from less than one percent a few weeks before.

But latest available federal data is weeks out of date, and modeling experts at CBC News said the true proportion of BA.4 and BA.5 cases is over 20 percent — and could be as high as 50 — with one likely to become dominant in the coming weeks.

“Over the past few years, COVID-19 has shown us that there could be even more surprises ahead,” Canada’s Chief Medical Officer Dr. Teresa Tam said at a press conference on Friday.

“The virus is still circulating in Canada and around the world, and factors such as virus evolution and weakening immunity are expected to influence COVID-19 activity in the future.”

Ready for a “Potential Resurgence”

Tam said Canada’s road ahead with COVID will not be easy, and officials are bracing for a “potential resurgence” that could have “major implications” down the road as Omicron sub-options struggle for dominance and new options could still emerge.

“Omicron has evolved and it’s very different from our vaccines and pre-Omicron infections — the type of immunity you have is just a different beast,” said Sarah Otto, an expert in modeling and evolutionary biology at the University of British Columbia.

“So what we’re seeing with vaccine protection is that it’s not so much the number of doses, but how recent your last dose was, and I think that’s because the neutralizing antibodies in our bloodstream, they don’t recognize either. virus”.

That’s why virologists and immunologists say that timing our next shots before a new potential wave, or when new options start to emerge in Canada, is so important that we don’t fall into the trap of trying to deploy doses in the midst of a rapidly deteriorating wave – for example, when Omicron first strike in December.

When should you get your 4th dose?

National Advisory Committee of Canada on Immunization (NACI) highly recommended second boosters for seniors aged 80 and over and other vulnerable groups back in April, but did not recommend a fourth shot for all Canadians.

The reason for this decision could be related to timing, with updated vaccines on the horizon that might work better against Omicron sub-variants, and quieter period of COVID activity in the summer we are buying time before another vaccine rollout may be needed.

But NACE management also recommends that those eligible wait for a second booster dose six months after the last dose, adding that timing “may need to be balanced with local and current epidemiology” and that “shorter intervals” may be needed if a new wave begins.

“When we start to see BA.4 and BA.5 lead to an increase in cases, I think we have to be nimble and expect that we need boosters – but this is a waiting game,” Otto said.

“The longer you wait to get a vaccine, the newer it will be and the stronger it will be when the next wave occurs. So you don’t want to get it months before the next wave – Canada needs to really push vaccines right. at the start of the wave.

Otto said Canada is likely to see another wave driven by BA.4 and BA.5, but it’s not yet clear how bad it is or if it’s already started, though some provinces like it Ontario as well as british columbia are seeing a recent spike in COVID wastewater surveillance.

Michelle Quick, 33, receives her second dose of Pfizer-BioNTech’s COVID-19 vaccine at a one-day makeshift clinic at the Eaton Center in Toronto on July 27, 2021. (Ewan Mitsui/CBC)

Updated vaccines may not be effective

Virologists and immunologists are also concerned that repeated revaccinations with COVID-19 vaccines adapted to the original strain of the virus may not be enough, and that updated vaccines may be needed to contain another potential wave in the coming months.

Modern bivalent vaccine This is one strategy that many have hopes for, but experts fear that targeting the original Omicron strain may not be enough due to research work demonstrating a lack of immunity to cross-protection against completely different BA.2.12.1, BA.4 and BA.5.

This experimental vaccine combines Moderna’s original vaccine with Omicron protection. preliminary data showed that it works, it has yet to be tested in the real world against the background of other sub-options.

WATCH | Moderna vaccine targeting Omicron shows promise:

Moderna’s “bivalent” amplifier can provide good protection, expert says

2 months ago

Duration 4:19

Toronto-based respirologist Dr. Sameer Gupta explains how Moderna’s planned new vaccine could provide broad protection against the coronavirus’ multiple mutations. The Moderna Dual Booster is currently in testing.

“I don’t think we’re going to see a significant benefit of Omicron-specific boosters over a conventional (original) strain booster,” Otto said.

“Either way, the boost helps because it raises antibody levels, but I don’t think it raises it enough to help us neutralize Omicron.”

“We need better long-term strategies”

University of Toronto immunologist Jennifer Gommerman says Omicron-specific boosters could be effective against sub-options of Omicron in the real world — but only if the virus doesn’t throw something else at us in the coming months.

“If Omicron is basically all the gimmicks that the virus left behind, then of course I think it makes sense to make vaccines based on Omicron because we have a very different virus now than we did at the beginning of the pandemic,” she said. .

“The concern will be that if the virus still has enough real estate to create a new version of itself that is really different from Omicron, then that’s not something we would like to take.”

Alison Kelvin, a virologist at the Canadian Center for Vaccinology and the Vaccine and Infectious Diseases Organization in Saskatoon, said the bivalent vaccine would protect against currently circulating sub-options of Omicron is a “big question.”

“At this point, I think we need to look forward to new options, whether it’s a new Omicron subline or a new variant altogether,” she said.

“We need better long-term strategies, and personally I don’t think a bivalent vaccine, from what we’ve seen with the virus, is a sustainable strategy. It’s about figuring out how we can cover more options at the same time to anticipate what’s coming next. option will be.”

Gommerman said nasal amplifierswhich are not yet available are likely to better protect against infection by targeting another part of the immune system, but some are still under development, including from the team at Macmaster University, they may still be years old.

WATCH | McMaster University is developing nasal vaccines against COVID-19:

McMaster University is developing inhaled aerosol vaccines against COVID-19

7 months ago

Duration 7:55

Professor Fiona Smale of McMaster University in Hamilton, Ontario, is testing two new inhaled aerosol formulations for a booster vaccine against COVID-19.

New options may change the timing of boosters

Canada now needs to decide whether the goal of its current-generation vaccine strategy is to protect against severe COVID or try to prevent transmission altogether, Gommerman said, until a new vaccine or variant changes the rules of the game.

“If your goal is to prevent infection, we’ll just have to keep pushing forever,” Gommemann said. “But if the goal is to protect the vulnerable, then we’re already doing that.”

Gommerman said she would not receive a fourth dose unless she knew there was a good public health reason to do so — for example, if COVID levels are rising, vulnerable groups are at risk, and the time frame is consistent with waning immunity against infection.

“But I know that my immune defenses in the form of immune memory will keep me out of hospital,” she said. “It won’t necessarily prevent me from being home for a week, but it will keep me away from the hospital, and that’s what vaccines were designed for.”

Otto said new variants will likely continue to emerge given the “huge variety of the virus that is supported around the world” and the fact that Omicron came out independently of other variants such as Alpha, Beta and Delta.

“We are already seeing this significant evolutionary change in Omicron — and all I want to say is don’t discount those other strains that are still circulating around the world,” she said.

“We’re playing Whac-A-Mole and we don’t know where the next mole will appear.”

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