No cause for concern about vaccines' efficacy against Delta variant, experts say

A recent surge in new COVID-19 cases linked to the new Delta variant in Israel is likely going to also play out in Canada, but there is no cause for concern just yet, according to experts. 

On Thursday, Quebec reported a total of 140 known cases of the Delta variant, first identified in India in April, which is nearly double the amount from the day before.

Meanwhile, health officials in Israel are not only seeing a surge in cases, but are now saying two doses of the Pfizer vaccine is only 64 per cent effective against infection from the variant, as opposed to 95 per cent effective against the original strain of the virus before the Delta variant popped up.

It’s just a matter of time before Delta, also known as B.1.617.2, becomes the dominant strain in Canada, said Dr. Christopher Labos, an associate with the McGill Office for Science and Society.

He said it’s likely that a Delta-driven surge could make its way in Quebec, but the key to avoiding another public health emergency is preventing a rise in hospitalizations, which is what the vaccines are designed to do.

“If you think about our situation, which is in many respects, very similar to what's going on in Israel right now as we open up society, as we allow international travel, as we relax the rules surrounding masks, it's very possible that we will see a surge in cases,” he said in an interview Wednesday.

“But as long as that surge in cases doesn't translate into more people in hospital, it's manageable, and that's the main objective of vaccines; they decrease infections -- that is undeniable. There's actually multiple studies showing that the vaccines still are effective against the Delta variant," he said.

"So looking at the Israeli data, I'm still somewhat reassured about the efficacy of vaccination against preventing a significantly worse fourth wave in this country and I think we can take away from this that the vaccines still are doing something very, very important.”

It’s not clear why the vaccine appears to be less effective at preventing infection, but one reassuring point is that Delta numbers in Quebec remain low compared to other jurisdictions. The Alpha variant, first identified in the U.K. is still the dominant variant in Quebec with 7,043 known cases, which have remained relatively stable in recent weeks.

Caroline Wagner, assistant professor in McGill’s Department of Bioengineering, said it’s still early to determine the exact reason for a decreased efficacy of the vaccines against the more transmissible Delta variant.

“The data that are coming out are definitely suggestive that Delta is more transmissible and that vaccine efficacy against infection is lower (particularly for one dose), but even the Israeli data suggests that protection against severe disease is still good, which I think is important,” Wagner told CTV News.

The longer a virus has time to spread, the more chances it has to mutate and become more transmissible, which is why experts say a successful vaccination campaign is key to ending the pandemic. Boosters could also become a reality, Wagner added, especially for immune-compromised people.

“The virus has demonstrated that it has evolutionary potential, and naturally that poses a potential threat to the efficacy of vaccines, but the mRNA platforms are also highly amenable to sequence updates,” she said.

“Ultimately, keeping infection numbers low globally, which means coordinated vaccine sharing, is the only way to really keep evolution at bay. The virus can’t evolve without infections.”

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