Pfizer vaccine highly protective against 2 COVID-19 variants, real-world data shows

By Lucas Casaletto

As Canada continues to see a rapid increase in deliveries and shipments of the Pfizer-BioNTech vaccine, a recent study shows that while the vaccine provides strong protection against two variants of concern (VOC), only one dose offers much less defense against the mutations.

According to new, real-world data out of Qatar, the study published in the New England Journal of Medicine discovered that the Pfizer-BioNTech vaccine (two shots) was roughly 90 percent effective at preventing infections caused by the B.1.1.7 variant, first discovered in the UK.

The B.1.1.7 strain is the most prevalent VOC in Ontario, with just over 83,000 cases detected up until Wednesday.

The study also found that efficacy dropped, if however insignificantly, to 75 percent against the B.1.351 variant that was first identified in South Africa. In comparison, the province has recorded 326 cases of that particular strain.

One key finding from the study was the level of protection people received after only one shot of Pfizer’s vaccine. It determined that one dose provides only 30 percent protection against the B.1.1.7 variant, falling even lower to 17 percent against South Africa’s strain.

Ontario’s Coordinator of Provincial Outbreak Response, Dr. Dirk Huyer, elaborated on the study’s findings Thursday, saying that from December 14 to April 19, the province reported an effectiveness of 70 percent in people after the first Pfizer dose.

“When I looked at the study, they didn’t specifically give the time frame after the first dose and we know that protection doesn’t begin until about 14 days [after a first shot],” said Huyer.

He added that protection could take even longer than 14 days through Pfizer’s shot, affirming the study’s findings that two doses offer the greatest level of protection from variants.

Experts and various studies have concluded that the B.1.351 VOC holds mutations that help it avoid specific antibodies, making it incredibly difficult to identify and has been found as the variant most likely to threaten the efficacy of vaccines.

“It really strongly emphasizes, with the variants, that need for the second dose,” Kathleen Neuzil, director of the Center for Vaccine Development at the University of Maryland School of Medicine, told the Washington Post.

“Which is a message we’ve been delivering, but now we have human clinical data to support that message.”

Ontario’s government said earlier this week it might shorten the length of time between COVID-19 vaccine doses as it prepares to receive more supply through May.

“We expect that with the much larger quantities of the Pfizer vaccines that we’re receiving throughout the month of May, that we may well be able to shorten the timeline for people to receive their second doses,” Health Minister Christine Elliott said.

Ontario is expected to secure half a million Pfizer shots through June.

Pfizer recommends a 21-day interval between its two shots, while Moderna recommends four weeks and Oxford-AstraZeneca advises between four and twelve weeks.

Though the latest study suggests Pfizer’s vaccine is less protective against that variant, it still offers strong protection, specifically against more severe or fatal cases of COVID-19.


RELATED: 


Notably, AstraZeneca and the University of Oxford’s vaccine was deemed ineffective against the B.1.351 variant in a small study, leading to South Africa opting against administering it.

The study also looked at Johnson & Johnson’s efficacy in the United States and in South Africa.

It showed that the J&J shot was 72 percent effective in the U.S. dipping to 64 percent in South Africa, likely due to the strong presence of the B.1. 351 VOC.

At their current rate of daily vaccinations, the province projects everyone aged 18-and-older will be able to book a vaccine appointment through Ontario’s online portal by the week of May 24.

Health Minister Christine Elliott said the revised vaccine target will mean 7.9 million people should have their first dose when the month ends.

Top Stories

Top Stories

Most Watched Today