The fall COVID-19 vaccine cut the risk of COVID-19 illness by about half overall, and by 67 per cent for those with a previous infection, according to new research from the Canadian network that has long tracked the performance of the annual flu shot.

This is the first time the Canadian Sentinel Practitioner Surveillance Network, which is comprised of hundreds of primary care providers in British Columbia, Alberta, Ontario and Quebec, produced mid-season estimates of the effectiveness of immunization against COVID-19.