Canada just approved one updated COVID-19 vaccine to target the first highly contagious Omicron variant, with doses expected to begin rolling out within days. But what exactly can we expect from these new shots when they land in the real world? The updated Moderna vaccine is a combination of two strains, known as a “bivalent” vaccine, that targets both the original virus and the Omicron BA.1 variant that emerged late last year and led to greater wave of infection and hospitalization in the pandemic. While the new download does not directly target the dominant Omicron BA.4 and BA.5 sub-variants, which The US approved an updated download for this week, Pfizer was submitted an application for Health Canada approval for Friday’s BA.4-5 vaccine and Moderna is expected soon. “The evidence we have to date shows that the BA.1 bivalent vaccine offers good protection against BA.4 and BA.5,” said Deputy Director of Public Health Dr. Howard Njoo during a technical briefing on Thursday. “Certainly, as the situation evolves, we’ll have to look at the evidence and see what happens to the effectiveness in the real world.” But what an updated booster can do for you depends on how vulnerable your immune system is, whether you’re one of the millions of Canadians recently infected with COVID, and when you were last vaccinated. WATCHES | Health Canada approves updated vaccine targeting Omicron variant:
Omicron variant vaccine approved by Health Canada
Health Canada has approved a new bivalent COVID-19 vaccine from Moderna that targets the Omicron variant. It’s the first vaccine of its type in Canada, but officials say another batch of booster shots, specifically targeting Omicron’s BA.4 and BA.5 subvariants, could arrive later this fall.
Will updated vaccines stop the spread of COVID?
Infectious disease experts, virologists, epidemiologists and immunologists hope the updated vaccines will be more effective at preventing transmission than the original vaccines — at least initially — but they also caution Canadians not to expect it to be a silver bullet. With limited data on the impact these vaccines will have, all eyes will be on their effect on slowing rates of infection and transmission, and whether they better protect vulnerable populations during the fall and winter months. “We don’t know what the impact is because it’s not available,” public health chief Dr. Teresa Tam said during a news conference Thursday when asked by CBC News how effective the updated vaccines will be in stopping the spread of the virus. Public health chief Theresa Tam said she was optimistic the new bivalent vaccine would boost protection against infection and transmission, at least until the fall. (Adrian Wyld/The Canadian Press) Tam said she hopes the new bivalent BA.1 vaccine from Moderna boosts protection against infection and transmission — at least until the fall. Clinical trial data for BA.1 vaccines from Modern and Pfizer-BioNTech suggests that they provide slightly stronger immune protection against Omicron than the original vaccines, but exactly what that translates to in the real world remains to be seen. “Immune responses to these variant boosters are modestly encouraging, but we still await definitive clinical evidence,” said Dr. David Naylor, who co-chairs the federal government’s COVID-19 Immunity Task Force. “That said, even if their marginal benefits are small, they could have a substantial positive impact if their innovation reignites public interest in stimulus.” A new preprint modeling studynot peer-reviewed, suggested that updated vaccines may not be much more effective than existing boosters in a population with hybrid immunity to vaccination and infection — especially when it comes to protecting against serious disease. But this could lead to significant population-level protection, with the preprint also suggesting that for every 1,000 people vaccinated with an updated booster, an average of eight fewer people would be hospitalized compared with the original vaccines. “We don’t yet know the magnitude of this improvement, but it will likely be quite limited,” said Dr. Gaston Des Serres, an epidemiologist at the National Institute of Public Health of Quebec (INSPQ). “Especially in the face of serious outcomes such as hospitalization for which, until now, the initial [vaccines] they were quite successful.”
What can updated COVID vaccines do for you?
More than half of Canadians have been infected with COVID since the emergence of Omicron and its highly contagious subvariants, and the added protection from prior infection in a vaccinated population appears to provide an advantage.
A new research letter published in New England Journal of Medicine examined the risk of BA.5 infection among individuals in Portugal who had prior infection with past variants, including BA.1 and BA.2, and found that they had strong protection against the newer variant.
This is partly because Portugal has such high levels of vaccination, with more than 98 percent of the population studied having at least two doses, meaning that like in Canada high levels of two-dose vaccination and infection provide strong immune protection .
Two Canadian preprint studies from May and Junewhich have not been peer-reviewed, also found that previous Omicron infections conferred strong immunity against future reinfection and hospitalization — especially when combined with vaccination.
“Generally we can predict that those who have hybrid immunity they’re going to be better protected,” said Dr. Danuta Skowronski, a vaccine effectiveness expert and chief of epidemiology at the BC Center for Disease Control and co-author of the preprints.
“And it’s also true that vaccine strains that better match the circulating variant will likely provide better protection.”
The longer you wait after your last infection or vaccination is also important to consider, as emerging evidence suggests that getting a booster too soon after infection or vaccination can affect vaccine effectiveness.
A new little one preprint studywhich has not been peer-reviewed, found that receiving a booster within two months of infection could negatively affect B cells that help build immune protection against serious illness.
NACI recommends waiting three months after infection before taking another shot, and three to six months between doses, but he also said in his most recent guidance that anyone at high risk of severe COVID in Canada should be offered a fall booster.
“Timing is everything, and generally the recommendations are to wait a few months after infection before getting a booster,” Skowronski said.
He added that people shouldn’t immediately rush to get a booster after infection because it could actually affect the immune response.
Updated vaccines ‘will help’, but no ‘miracle’
Canada still has a “worrying gap” in third-dose coverage, Naylor said, with less than half of Canadians having received a booster even though it provides significant additional protection against severe COVID-19. Only for 12 percent have received a fourth dose. “As we start to head into fall and almost certainly start to see cases pick up again, the updated booster is definitely going to be better than no booster at all,” said Deepta Bhattacharya, a professor of immunobiology at the University of Arizona. . “Since the BA.5 is still around, I don’t really see any downside to collecting these amps, and they’ll probably work better than another take on the original.” Fewer than half of Canadians have received a booster, even though it provides significant additional protection against severe COVID-19. Only about 12 percent have received a fourth dose. (Darryl Dyck/The Canadian Press) Bill Hanage, an epidemiologist at the Harvard TH Chan School of Public Health in Boston, said it’s important to keep in mind that although the original vaccines were far from an exact match for Omicron – they still provided strong protection against serious disease. “But closer matches now will have to do more,” he said in an email. “Notably, there may be a period after the vaccine when people are immune to infection.” Bhattacharya said the “big question” on the mind right now is how effective the updated vaccines will be at stopping transmission in the real world — and for how long. “Are we starting to restore some of the protection against any infection or symptomatic infection with these boosters? I expect we will,” he said. “Just how long that effect will last, I think, remains to be determined.” Dr. Allison McGeer, a medical microbiologist and infectious disease specialist at Toronto’s Mount Sinai Hospital, said the updated shots may provide a small boost to neutralizing antibodies that can prevent transmission — and that the added protection is “nothing.” . “An extra dose of the original vaccine results in significantly increased protection against BA.4 and BA.5. It’s not perfect, but I think we’re discovering that nothing is perfect,” he said. “Bivalent vaccines, they might be a little bit better, but they’re not going to be a miracle.” Bhattacharya said that while the clinical trials showed only a two-fold increase in protective antibodies against the BA.1, BA.4 and BA.5 variants that Moderna and Pfiizer are targeting in their bivalent vaccines — it’s still significant protection. “If you look at the data, it’s a ton more antibodies being produced,” he said. “So I have every reason to expect that they will help — and probably help a lot.”
