The timing of your next COVID-19 vaccine may be more important than ever, as highly contagious Omicron subvariants are on the rise in Canada, and declining immunity from previous vaccinations and infections threatens to fuel another increase. .
Canada is once again a focus of variants, with BA.2.12.1 now accounting for more than 40% of COVID cases, while BA.4 and BA.5 are rapidly gaining ground at more than 10% combined by the end of May. a significant jump from less than a hundred weeks earlier.
But the latest federal data available is out of date weeks ago and CBC News modeling experts spoke to estimate that the actual proportion of cases BA.4 and BA.5 is more than 20 percent, and could reach 50, with one of them likely to happen dominant in the coming weeks.
“COVID-19 has shown us over the last few years that there may be more surprises ahead,” Canada’s director of public health, Dr. Theresa Tam, told a news conference on Friday.
“The virus is still circulating in Canada and internationally and factors such as viral progression and decreased immunity are expected to affect COVID-19 activity in the future.”
Preparing for a “potential resurgence”
Tam said the road to Canada with COVID will not be easy and that officials are preparing for a “potential resurgence” that could cause “serious impacts” in the future, as Omicron’s sub-variants are fighting for dominance and still new variants could emerge.
“Omicron has evolved and is very different from our pre-Omicron vaccines and infections: the kind 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 as the recent one that has been your last dose, and I think it’s because the neutralizing antibodies in our bloodstream, not they are also recognizing the virus. ”
That’s why virologists and immunologists say it’s so important to schedule our next shots before another potential wave or when new variants start to rise in Canada, so they don’t catch us fighting to throw doses in the middle. a rapidly worsening wave, such as When Omicron first hit in December.
When should you receive a fourth dose?
National Immunization Advisory Committee of Canada (NACI) According to highly recommended reinforcements for people aged 80 and over and other vulnerable groups in April, but failed to recommend a fourth injection for all Canadians.
The reason for this decision may have been reduced to the moment, with up-to-date vaccines on the horizon that could work better against Omicron sub-variants, and a quieter stretch of COVID activity in the summer that will allow us gain time before another vaccine is needed.
But the NACI guide He also recommends that eligible people wait six months after their last dose for a second booster, adding that the time “may need to be balanced with local and current epidemiology” and that “intervals may be needed.” shorter “if another wave arrives.
“When we start to see that BA.4 and BA.5 lead to growing cases, then I think we should be agile and expect that we need to get the reinforcements, but it’s that waiting game,” Otto said.
“The longer you wait to receive the vaccine, the more recent it is and the more powerful it will be when the next wave passes. So you don’t want to receive it months before the next wave: Canada should promote vaccines properly. a wave “.
Otto said that Canada will probably see another wave driven by BA.4 and BA.5, but it is still unclear how far it will go and whether it has already begun, although some provinces such as Ontario i British Columbia We are seeing a recent rise in COVID wastewater monitoring.
Michelle Quick, 33, receives her second dose of the Pfizer-BioNTech COVID-19 vaccine at an emerging one-day clinic at the Eaton Center in Toronto on July 27, 2021. (Evan Mitsui / CBC )
Updated vaccines may be short
Virologists and immunologists are also concerned that repeated reinforcements with COVID-19 vaccines adapted to the original strain of the virus are no longer sufficient, and that updated vaccines may be needed to stop another potential wave in the coming months.
Modern bivalent vaccine It’s a strategy many are hoping for, but experts are concerned that targeting the original Omicron strain may not be enough. research showing a lack of cross-protection immunity against the very different BA.2.12.1, BA.4 and BA.5.
This experimental vaccine combines Moderna’s original vaccine with protection against Omicron and while preliminary data proved that it seemed to work, it has not yet been tested in the real world with the other subvariants.
TARGET | Moderna’s Omicron vaccine is promising:
Moderna’s “bivalent” reinforcement can provide good protection, the expert says
Dr. Samir Gupta, a Toronto respirator, explains how Moderna’s planned new vaccine can offer comprehensive protection against multiple coronavirus mutations. Moderna’s dual variant reinforcement is currently being tested.
“I don’t think we’ll see a significant advantage of a boost from a specific Omicron boost than just a regular boost with the (original) strain,” Otto said.
“Either way, the boost helps because it increases antibody levels, but I don’t think it increases it much more in a way that helps us neutralize Omicron.”
“We need better long-term strategies”
University of Toronto immunologist Jennifer Gommerman says specific Omicron enhancements may be effective against real-world Omicron subvariants, but only if the virus doesn’t launch anything else in the coming months.
“If Omicron is basically all the tricks the virus has left, then for sure, I think it makes sense to make Omicron-based vaccines because we now have a very different virus than we had at the beginning of the pandemic,” he said. .
“The concern would be if the virus still has enough real estate to make a new version of itself that is really different from Omicron; then that would not be what we would like to take.”
Alyson Kelvin, a virologist at the Canadian Vaccine Center and the Saskatoon Infectious Vaccine and Disease Organization, said whether or not a bivalent vaccine will protect against circulating Omicron variants is a “big question.”
“At this point, I think we should expect new variants, either a new Omicron underline or a new variant as a whole,” he said.
“We need better long-term strategies, and I personally don’t think a bivalent vaccine is, from what we’ve seen of the virus, a sustainable strategy. It’s about figuring out how we can cover more variants at once to predict what the next one will be. will be”.
said Gommerman nasal reinforcementswhich are not yet available, will probably better protect against infection by targeting a different arm of the immune system, but while there are several in development, including a team of McMaster University, they could still be years away.
TARGET | McMaster University develops nasal vaccines against COVID-19:
McMaster University is developing inhaled aerosol COVID-19 vaccines
Professor Fiona Smaill of McMaster University in Hamilton, Ontario, is conducting trials of two new inhaled aerosol drugs intended as COVID-19 booster vaccines.
New variants could change the time of the drivers
Canada now has to decide whether the goal of its current-generation vaccine strategy is to protect against serious COVID or try to prevent transmission altogether, Gommerman says, until a new vaccine or variant changes the game.
“If your goal is to prevent infection, we need to keep increasing it forever,” Gommeman said. “But if the goal is to protect the vulnerable, we have already done so.”
Gommerman said he would not receive a fourth dose unless he knew there was a compelling public health reason for doing so, as if COVID levels were rising, vulnerable groups were at risk and the time period was aligned against decreased immunity to infection.
“But I know my immune protection in the form of immune memory will keep me out of the hospital,” he said. “It won’t necessarily stop me from being home for a week, but it will keep me out of the hospital and that’s why the vaccines were designed.”
Otto said new variants will likely continue to emerge, given the “large amount of virus diversity that remains worldwide” and the fact that Omicron emerged independently of other variants such as Alpha, Beta and Delta.
“We’re already seeing this substantial evolutionary change in Omicron, and all I’m saying is, don’t discount those other strains that are still circulating globally,” he said.
“We’re in a Whac-A-Mole game and we don’t know where the next mole will come from.”