The BA.5 subvariant still accounts for more than 90 per cent of all COVID-19 cases in Ontario but experts are now keeping a close eye on the spread of two other subvariants which they say could end up factoring into the next wave of the pandemic.

The BQ.1.1 and BA.2.75.2 subvariants are both raising concerns in scientific circles because of mutations that could help them more effectively evade immunity from vaccination and prior infection.

Both subvariants, it should be noted, only account for a fraction of COVID-19 cases that have been sequenced globally so far.

But in a story published last week, Science magazine warned that “one or more may well cause big, new COVID-19 waves this fall and winter.”

Meanwhile, in Ontario viral activity could already be ticking up without either subvariant spreading widely.

That has led to concerns about what the next few months could look like, especially if a new subvariant eventually becomes dominant.

“Even if we just had bad old BA.5 we still probably would have a rise in cases because you've got some people who haven't been infected yet, you've got waning protection of vaccines with time and you have a lot of people in indoor settings and we know that is where the virus is transmitted,” infectious diseases specialist Dr. Isaac Bogoch told on Monday. “The thing that concerns me, though, is that our healthcare system just isn't as well equipped as it has been in the past to care for these additional stresses.”

Here is what you need to know about BQ.1.1., BA.2.75.2 and what the next few months could look like in Ontario:

What is concerning about BQ.1.1. and BA.2.75.2?

Both BQ.1.1. and BA 2.75.2 feature mutations that could help them better evade immunity and drive new COVID-19 waves. Bogoch said that both subvariants could spell trouble for vulnerable populations as initial research suggests that they are capable of evading some of the protection provided by a popular antibody drug often prescribed to people who are “significantly immunocompromised” and unable to receive a COVID-19 vaccine.

“There are people on various chemotherapies or transplant recipients who receive an antibody cocktail called Evusheld and it is really important. It provides them with several months of protection against COVID-19. But with BQ.1.1 it doesn’t look like that treatment would be as effective if it takes over,” he told

While BQ.1.1. and BA.2.75.2 may be able to evade some of the immunity provided to individuals who take Evusheld, initial data does suggest that other antiviral treatments like Pfizer's Paxlovid pill hold up relatively well against the new subvariants.

Will either subvariant become dominant?

That is the million dollar question. So far only 23 instances of BA.2.75.2 have been confirmed through sequencing in Ontario but its share of cases is growing quickly in India, where it was first detected. BQ.1.1, meanwhile, has not been detected in Ontario at this point. That said, it has accounted for an increasing share of lab-confirmed cases in the United Kingdom and at least one virologist recently took to Twitter to predict that it will “drive a variant wave in Europe and North America before the end of November.”

“Most of these mutations will amount to absolutely nothing but once in a while you might get a mutation that does amount to a variant that may outcompete the existing variants and this one (BQ.1.1) seems to have gained at least a little bit of a foothold in the U.K. and maybe some other parts of Europe,” Bogoch told “It is certainly one that is important to keep an eye on.”

What about vaccines? Will they still work against new subvariants?

Health Canada approved a new bivalent vaccine specifically targeted against Omicron for adults 18 and older last month. While that vaccine was tailored towards the initial strain of Omicron, Health Canada has said that the shot should still provide a “stronger immune response” against more recent subvariants, including BA.5. While it is not clear what level of protection vaccines may provide against BQ.1.1. or BA.2.75.2, Bogoch said that there is no reason to believe that either are sufficiently different enough to completely diminish the protective benefits of vaccination.

“So far with every single variant we have seen, Alpha, Delta, Omicron BA.1, Omicron BA.2, Omicron BA.5, with every single variant the vaccines have continued to do a remarkable job protecting us against severe infection, such as hospitalization and death,” he said. “So when we are talking about some of these variants rolling through town it is not as if we are immunonaive. We are not. The vast majority of the Canadian public has either been vaccinated, recovered from infection or both.”

Is a new subvariant or variant becoming dominant inevitable?

Quite possibly. There have been five different variants of concern declared by the World Health Organization since the onset of the pandemic, four of which became dominant in Ontario at one point or another. Bogoch said that while new variants do emerge from time to time, it is his hope that “these waves will hopefully have less and less of an impact on Canadian society” as we increase our level of immunity, both through vaccination and antibodies developed through infections.

“This is just what viruses do. Viruses have a predictable rate of mutation and the virus continues to mutate. Some mutations might result in a more fit virus, most mutations result in nothing whatsoever but some might create a more fit virus that either evades some of our protective immunity or is more transmissible and those viruses will ultimately become the dominant viruses in various communities,” he said. “It has happened several times before and it might happen again.”

What can we expect this fall and winter?

Wastewater surveillance has shown that COVID-19 viral levels have been on the rise in most parts of Ontario since around the second week of September. Other public health indicators, including hospitalizations, have also begun to worsen in recent weeks. Speaking with CP24 on Wednesday, Toronto’s Medical Officer of Health Dr. Eileen de Villa said that officials are watching wastewater surveillance and hospital admissions closely but she said that residents still need to do their part to reduce transmission.

“As much as so many of us want to be done (with) the pandemic it is not yet done with us,” she said. “The good news is we have lots of tools at our disposal. So staying home when you are sick or have symptoms of illness, washing your hands, wearing masks especially when indoors with lots of people and of course where it is possible gathering outside is still a safer option.”