Canadian infectious disease specialists are now saying that people who receive regular flu shots are at risk of increased infection with pandemic flu.
During the 2009 H1N1 pandemic, researchers at the B.C. Centre for Disease Control originally thought seasonal flu shots from 2008 might offer extra protection against the new pandemic strain. They were puzzled to find instead, seasonal flu vaccination almost doubled the risk of infection with pandemic flu.
Dr. Danuta Skowronski and her colleagues went on to do five more studies during the summer that showed the same effect in people and in ferrets, which are considered the best animal model of flu.
“This was a unique finding in a unique context of dramatically mismatched vaccine to novel pandemic influenza virus,” she said.
What was originally called ‘the Canadian problem’ of higher risk of pandemic flu illness among those who received seasonal flu shots the year before has since been observed in other countries. (Spencer Platt/Getty)
She recalled the intense time, struggling to find answers about whether to offer the seasonal as well as pandemic vaccine in the fall. “That was the worst summer I think of my life, work wise.”