Flu shot less than 20% effective for most common strain this season, scientists find
Early results in line with what Australia experienced during the Southern Hemisphere's flu season
The Canadian Press Posted: Feb 01, 2018 2:39 PM ET Last Updated: Feb 01, 2018 4:07 PM ET

The effectiveness of this season's flu shot has been extremely low, with the vaccine preventing only 10 to 20 per cent of infections caused by the dominant H3N2 strain affecting Canadians, researchers have found.

The mid-season estimate for the vaccine's ability to provide protection from this particular influenza strain is in line with what Australia experienced during the southern hemisphere's flu season, which ended in late August as Canada's was about to begin.

"That means people who were vaccinated should not consider themselves invincible for this season," said lead researcher Dr. Danuta Skowronski, an infectious diseases expert at the BC Centre for Disease Control.

Both Canada and Australia used the same vaccine components, which were meant to offer protection against two A-type influenza viruses ?H3N2 and H1N1 ?​ and a B strain.

The same vaccine was used last season in Canada and found to be 42 per cent effective in preventing cases of H3N2 in this country.

But because the virus appears to have genetically mutated somewhat since then, the vaccine is less effective this year...