If you received a flu shot this season and still ended up sick with the influenza virus, you would be in the majority.
Researchers at the B.C. Centre for Disease Control says the effectiveness of the vaccine has prevented between 10 to 20 per cent of infections.
The shot is meant to offer protection against the H3N2 and H1N1 A-type viruses and a B-type strain.
It is the same vaccine that had a 42 per cent effectiveness last year in preventing the dominant H3N2 strain.
Scientists say that is a sign the virus has genetically mutated and has made the vaccine less effective.
Lead researcher Danuta Skowronski says the dominant B strain that causes respiratory illness has been prevented in 55 per cent of flu shots this season.
The findings of the mid-season research are published in the online journal Euro Surveillance.
With files from the Canadian Press.