Tests on donated blood have found that immunity against COVID-19 among vaccinated Canadians and those who have already contracted the virus has been waning throughout the population.
Tests on around 9,000 donated blood samples show that antibodies in the blood which fight the virus declined in October in 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 Taskforce says that the highly contagious Omicron variant may offer an ``immune dividend'' giving a boost against future infection.
Scientists on the taskforce are now studying the extent of immunity offered to people infected with Omicron, as well as immunity in vaccinated people's cells which can kick in to fight future COVID-19 infections.
Their findings are likely to influence when and how many booster shots people may have in future.