Does the updated COVID-19 vaccine protect against the XEC variant?

Pharmacist Kim Nguyen administers a Moderna Spikevax COVID-19 vaccine at a CVS, Wednesday, Sept. 20, 2023, in Cypress, Texas. (Melissa Phillip/Houston Chronicle via AP)

We're in the middle of flu season, and a new variant of COVID-19 is making its way through Canada.

The XEC strain, a hybrid of Omicron subvariants KS.1.1 and KP.3.3, was first detected in Canada in mid-August and the number of COVID-19 cases with the XEC variant has rapidly increased.

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According to the most recent data from the Public Health Agency of Canada, the proportion of positive cases with the XEC variant as of Oct. 13 was 18.9 per cent, up from just 3.1 per cent of cases on Sept. 1. The strain with the most cases is the Omicron KP.3.1.1 variant, which accounts for 48.4 per cent of all COVID-19 cases.

Isaac Bogoch, an infectious diseases specialist at Toronto General Hospital, says a virus mutating into different variants is normal.

"We've seen multiple variants through the last almost five years," Bogoch said. "It just means the virus is changing as expected. I think if people are wondering what does this actually mean, it's always difficult to predict the future. But this upcoming winter is likely going to look very similar to last winter from a COVID-19 standpoint."

Does the new vaccine protect against XEC?

Health Canada approved Pfizer-BioNTech's updated COVID-19 vaccine in September, which is now available for use across the country.

However, it was developed before the XEC variant hit the general public.

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Bogoch says the latest vaccine was designed for a sublineage of Omicron called KP.2, which began circulating several months ago. While it may not be a perfect match to combat the XEC strain, he says each new updated vaccine more closely resembles the circulating mutations of the COVID-19 virus.

"It's always going to be an arms race of the virus mutating and creating a vaccine that's adapted to it," Bogoch said, adding that it's very similar to the influenza vaccine that's updated each year. "You're never going to get it perfect."

Bogoch says since the start of the pandemic, regardless of the vaccine and the active COVID-19 strain that is circulating, "all of the vaccines have done a remarkable job in reducing the risk of severe infection, such as hospitalization and death," especially for those who are most vulnerable.

"It doesn't have to be a perfect match, but we know the vaccines are still pretty darn good."

Bogoch says while we're beyond the era of mask mandates, people can choose to wear one in an indoor setting to reduce their risk of getting sick and that, if possible, people should stay home when sick to prevent others from also getting ill.