Effectiveness of flu shot this season has been extremely low


Researchers have found that this season the effectiveness of flu shots has been extremely low with findings indicating that only 10-20 per cent of infections caused by dominant H3N2 strain are being prevented.

This effectively means that even though people may have got their flu shots, they aren’t invincible for this season, experts have warned.

Last season the effectiveness of the vaccine was double than this season’s – i.e. at 42 per cent. But because the virus appears to have genetically mutated since then, that’s likely made the shot less effective this year.

Vaccine efficacy was determined by comparing positive influenza tests in vaccinated and unvaccinated patients who sought care at community-based practitioners in British Columbia, Alberta, Ontario and Quebec, representing 80 per cent of the population. These providers make up the Canadian Sentinel Practitioner Surveillance Network that monitors how well the influenza vaccine protects people from influenza.

Network researchers analyzed the data and found that overall, the flu shot was 17 per cent effective in preventing the respiratory illness from the H3N2 virus, but only 10 per cent effective for working-age adults 20 to 64. Join our Rewards Program to earn points and benefits.

If we put these findings in quantitative figures, out of the 100 who have opted for the vaccination only 10 are effectively protected and 90 of those would still get sick.

However, scientists did say that the vaccine was 55 per cent effective overall in preventing cases of the respiratory illness caused by the dominant influenza B strain also affecting Canadians this season. In working-age adults, it was 40 per cent effective.

That strain is known as B/Yamagata. But interestingly, the component in the vaccine is B/Victoria — which has a completely distinct viral lineage from B/Yamagata. A 55 per cent vaccine effectiveness suggests there is good cross-protection between the two B strains, researchers added.

Scientists have warned that Canadians can’t rely solely on the vaccine to protect them from coming down with the flu this season and they have to opt for other protective measures like washing hands often with soap and water to minimize contamination need to be adopted.

Visits to long-term care homes should also be avoided because the elderly have the greatest risk of getting sick from the H3N2 virus and developing complications that can lead to hospitalization or even death. Join our Rewards Program to earn points and benefits.


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