Omicron could boost waning virus immunity, government advisers say

OTTAWA — Immunity against COVID-19 among vaccinated adult Canadians and those who have already contracted the virus has been waning throughout the population, tests on donated blood have found.

Tests on about 9,000 donated blood samples from across Canada show that antibodies in the blood that fight the virus declined in October among all age groups, with experts saying the waning immunity is likely to have continued in November and December.

But the head of the government’s COVID-19 Immunity Task Force says that the highly contagious Omicron variant might offer an “immune dividend” offering fresh protection against future infection.

Scientists on the task force are now analyzing the extent of immunity offered by Omicron, as well as “memory of immune protection” in the cells, which can kick in with future COVID infections.

With the task force studies of immunity levels informing government policy on booster shots, the findings are likely to influence when and how many booster shots people might have in future.

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

“There are large sections of the population that are now infected with Omicron and therefore this is one of the priorities for the task force, to understand what the immune dividend is from infection from Omicron,” he told the Canadian Press.

“If it is strong and sustained in terms of immune memory it may have an impact on how we think about the need and timing of boosters.”

Evans added that Omicron is now so widespread that “our testing systems can’t keep pace.”

“So the number [with Omicron] is vastly underestimated. There are large sections of the population that are now infected with Omicron,” he said.

Canadian Blood Services is testing the presence of antibodies that fight COVID-19 in blood samples from donors over 17 years of age every month. It detected a big immunity boost last summer after Canadians got their second vaccine shot.

But in September, the blood agency noticed that antibodies that could fight the virus were waning in people over the age of 70.

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