People who receive flu vaccines year after year can sometimes show reduced protection, an effect that Canadian infectious disease specialists say muddies public health messages for annual flu vaccine campaigns. 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. 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. What was originally called the Canadian problem" has since been found in a randomized control trial by researchers in Hong Kong ... Japan and the U.S. Researchers in several countries have found a blunting or "interference" effect between previous seasonal vaccines and reduced levels of vaccine protection in later years. "People do not have a good explanation for why," said Dr. Michael Gardam, director of infection prevention and control at Toronto's University Health Network. "We have kind of hyped this vaccine so much for so long we are starting to believe our own hype. Really, what we should be doing is looking for better vaccines," Gardam said. In the meantime, public health officials who aim to protect people from flu complications need to grapple with the imperfections of a vaccine given every year to a moving target of strains.