Canadian researchers say this season's influenza vaccine appears to be highly effective. A mid-season analysis shows this year's flu vaccine is 72 per cent effective in preventing infection with the H1N1 respiratory virus. The BC Centre for Disease Control says that level of protection against H1N1 was observed across all age groups, including children who are especially vulnerable. The agency says the influenza vaccine tends to perform better during seasons dominated by H1N1 Last season's flu shot was less than 20 per cent effective in preventing Canadians from getting sick during what turned out to be an H3N2-dominant epidemic.