Previous infection poor protection against Omicron: U of S study

"This is a new variant. It needs better antibody levels, and the best way to get those antibodies is from vaccines.”

Zak Vescera 4 minute read January 18, 2022

University of Saskatchewan researchers spent part of the winter holidays using blood, monkey cells and viral samples to see how different defences stack up to the new Omicron variant of COVID-19.

Their results, released in a preprint that has yet to be peer reviewed, found vaccination creates a stronger response to the Omicron variant compared to antibodies from prior COVID-19 infection, creating yet another reason to get the jab as the new strain takes over in Saskatchewan.

“If you’ve been infected, don’t believe you’re protected,” Dr. Arinjay Banerjee said.

Dr. Arinjay Banerjee is a researcher at the Vaccine and Infectious Disease Organization at the University of Saskatchewan. Courtesy David Stobbe / Courtesy David Stobbe

“Our data clearly shows that exposure alone, it does not induce enough antibodies against Omicron. This is a new variant. It needs better antibody levels, and the best way to get those antibodies is from vaccines.”

As Omicron emerged, Banerjee and colleagues at the Vaccine and Infectious Disease Organization wanted to understand whether people with previous infection, vaccination or both would be protected.

“People basically cancelled their Christmas holidays and they came in,” Banerjee said.

To propagate the virus, researchers introduced different strains to African green monkey cells and allowed them to spread. Then, in a high-level, specialized laboratory, they introduced the viral strains to 65 blood samples and measured the antibody response.

Darryl Falzarano was one of the researchers who spent part of his holiday studying the Omicron variant of COVID-19. Matt Smith / Saskatoon StarPhoenix

The results of the study are not a perfect simulation for real life. Antibodies are only one “piece of the puzzle” in the human immune system, Banerjee said, and scientists still don’t know what level of antibodies will be perfectly protective against COVID-19.

The results found antibody responses were stronger in blood samples from long-term care residents who had received a third “booster” dose of vaccine compared to people who had a previous infection with the Delta or “ancestral” strain of COVID-19. They were also stronger in people who had been infected and then received two doses of vaccine.

Banerjee said antibody responses were weaker against Omicron than they were against the Beta or Delta strains of COVID-19, which researchers also used.

VIDO researchers have been working on a COVID-19 vaccine since January 2020. Michelle Berg / Saskatoon StarPhoenix

“I don’t want to say that prior infection is offering zero protection, because I don’t think that’s the case. But it’s certainly not providing a high level of protection,” said Dr. Darryl Falzarano, a veterinary microbiologist at VIDO who also worked on the study.

“To get better protection than that, you need a higher-level immune response than you would against the ancestral virus — and to get that, I think you need that third dose.”

Falzarano said part of the challenge of studying COVID-19 is that the virus mutates faster than researchers can keep up. Some studies on the Delta variant are just now coming out, even though Delta has been replaced in much of the world, he noted.

Scientists do not yet know of a “magic number” of neutralizing antibodies that protect against the virus, in part because it keeps changing, he said.

“I think that would be an important thing to figure out. It’s just that’s very difficult to do, especially since the variants keep changing.”

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