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 waning immunity from previous vaccination and infection threatens to fuel another surge.
Canada is once again a hotbed for variants, with BA.2.12.1 now making up more than 40 per cent of COVID cases, while BA.4 and BA.5 are quickly gaining ground at more than 10 per cent combined in late May — a major jump from less than one per cent weeks earlier.
But the latest available federal data is weeks out of date and modelling experts CBC News spoke to estimate the true proportion of BA.4 and BA.5 cases is more than 20 per cent — and could be as high as 50 — with one of them likely to become dominant in the coming weeks.
“COVID-19 has shown us over the past few years that there may be more surprises ahead,” Canada’s Chief Public Health Officer Dr. Theresa Tam said during a press conference Friday.
“The virus is still circulating in Canada and internationally and factors such as viral evolution and waning immunity are anticipated to impact COVID-19 activity moving forward.”
Bracing for ‘potential resurgence’
Tam said Canada’s path forward with COVID will not be straightforward, and officials are bracing for a “potential resurgence” that could lead to “severe impacts” in the future as the Omicron subvariants battle for dominance, and new variants could still emerge.
“Omicron has evolved and it’s so much different than our vaccines and infections prior to Omicron — the type of immunity that you got is just a different beast,” said Sarah Otto, an expert in modelling and evolutionary biology at the University of British Columbia.
“And so what we’re seeing with vaccine protection is that it’s not so much the number of doses as it is how recent your last dose has been, and I think that’s because the neutralizing antibodies in our bloodstream, they’re not recognizing the virus as well.”
That’s why virologists and immunologists say timing our next shots ahead of another potential wave or when new variants start to rise in Canada is so important, so we don’t get caught scrambling to roll out doses in the midst of a rapidly worsening wave — like when Omicron first hit in December.
When should you get a 4th dose?
Canada’s National Advisory Committee on Immunization (NACI) strongly recommended second boosters for seniors aged 80 and up and other vulnerable groups back in April, but stopped short of recommending a…