Omicron could boost waning immunity, blood tests show

OTTAWA – Immunity to COVID-19 among vaccinated adult Canadians and those who have previously contracted the virus has declined across the general population, tests of donated blood have revealed.

Tests on around 9,000 blood samples donated across Canada show that antibodies in the blood that fight the virus declined in October across all age groups, with experts saying the decline in immunity has worsened. probably continued in November and December.

But the head of the government’s COVID-19 immunity task force said the highly contagious variant of Omicron could offer an “immune dividend” offering new protection against future infection.

Scientists in the task force are now analyzing the extent of immunity offered by Omicron, as well as the “immune protection memory” in cells that can be triggered with future COVID-19 infections.

With the Immunity Levels Working Group studies informing government policy on booster shots, the results are likely to influence when and how many booster shots people might receive in the future.

Dr Tim Evans, executive director of the task force, which is advising the government on its response to the pandemic, said in an interview that studying immunity due to Omicron is now a priority.

“Large swathes of the population are now infected with Omicron and so it is one of the priorities of the working group to understand what the immune dividend is from infection with Omicron,” he told La Canadian Press.

“If it’s strong and sustained in terms of immune memory, it can impact how we think about the need for and when to boosters.”

Evans, added that Omicron is now so widespread that “our test systems cannot keep pace.”

“So the number (with Omicron) is vastly underestimated. Large swathes of the population are now infected with Omicron,” he said.

Canadian Blood Services tests blood samples from donors over the age of 17 every month for the presence of antibodies that fight COVID-19. He detected a surge in immunity last summer after Canadians received their second vaccine. But in September, he noticed that the antibodies able to fight the virus were declining in people over 70.

A Canadian Blood Services report completed this week, analyzing blood donated in October, shows that among all donors, from 17-year-olds to retirees, immunity has waned.

Sheila O’Brien, associate director of epidemiology and surveillance at Canadian Blood Services, said she was “uniquely positioned to provide information on the presence of COVID-19 antibodies in a large number of people across Canada relatively quickly ”.

She said antibodies able to fight the virus were significantly higher in people who were vaccinated than in people who were not vaccinated.

“About 2 weeks after vaccination, antibody levels peak and then gradually decline,” she added.

Evans predicted that the decline in immunity, measured in blood, would continue to show up in data for November and December. But he said the task force will investigate whether there has been an increase in immunity with more and more people contracting Omicron.

The findings of the Waning Immunity Task Force prompted the government to offer booster shots to vulnerable groups such as transplant patients with weaker immunity and the elderly.

Dr Bruce Mazer, immunologist and associate scientific director of the COVID-19 Immunity Task Force, said that even with decreasing levels of antibodies in the blood, the body’s immune system has a cellular memory of a virus and can mobilize to fight it. He said people who have been vaccinated, have had the virus, or both, generate cellular immunity.

“Other parts of the immune system wait and act as sentries,” he said. “You have T-cell memory that helps fight the virus, and B-cell memory that helps make new groups of antibodies.”

The McGill professor said the working group is currently studying this rescue immune response, as well as the immune response to the Omicron variant which he says has 50 mutations, from the original COVID-19 virus.

This report by The Canadian Press was first published on January 6, 2022