The BA.5 subvariant can evade protection, but there are still tools to fight it

A highly transmissible variant of the coronavirus is spreading through Canada, driving another wave of infections, even among those who have recently recovered from COVID-19.

The Omicron subvariant BA.5, and to a lesser extent, BA.4, is largely behind the latest wave — the seventh of the pandemic and the third since the arrival of Omicron. 

Both have shown an ability to evade the protection offered by previous infection. 

"The BA.5 subvariant has mutated to the extent that your body is not recognizing it and people are getting reinfected," said Dr. Fahad Razak, an internist at St. Michael's Hospital in Toronto and the scientific director of Ontario's COVID-19 Science Advisory Table.

"So you're seeing this additional surge start in Ontario, and now it's started in other parts of Canada as well."

The good news is that data emerging from countries where BA.4 and BA.5 have already taken hold, such as South Africa, suggest they are not more severe than previous Omicron subvariants or more likely to lead to hospitalizations.

Still, the sheer number of people likely to get sick (particularly those vulnerable to serious illness), coupled with the overtaxed emergency rooms in many parts of the country, is cause for concern, Razak said.

"Something that's a little bit less severe but infects a lot of people means … that the total number of Canadians who get sick — very sick and potentially die — can actually be higher," he said.

Razak pointed to a scientific analysis conducted for the Toronto Star, which found that since mid-2021, Omicron has been more deadly for Ontarians aged 60 and over than the previous two waves combined due to the high volume of infections.

Razak is now among a chorus of experts and public health officials urging the Canadian public to get a booster for protection against more serious illness.

"That third dose is incredibly valuable," he said. "It gives you protection against severe disease and will give you at least a few weeks, maybe a couple of months, for protection against even getting infected at all.

"So if you haven't received that third dose, there's no better time than now."

Canada had one of the highest vaccination rates in the world after two doses, but uptake on subsequent shots has been slower. Across Canada, more than 40 per cent of eligible Canadians have not yet received a third dose. 

Razak says the messaging around what constitutes being "fully vaccinated" needs to change, given the evolution of the virus and the waning immunity of the vaccines over time.