imageThis year’s flu vaccine is offering limited protection in the United States against the virus responsible for a major wave of illness currently crashing over North America, a new report from the U.S. Centers for Disease Control suggests. A corresponding assessment of how effective the vaccine is in Canada this winter is still in the works. But there is good reason to believe the Canadian estimates will be at least as bad when they are published, probably later this month, experts say.  The study calculated how much protection the vaccine offered against getting sick enough to require medical care. (Most people who catch the flu tough it out without seeing a doctor, making them impossible to study.) It found that so far this year the vaccine is, on average, lowering that risk by 23 per cent, across all age groups and all the types of circulating flu viruses. When the scientists look specifically at H3N2 viruses — far and away the most dominant virus type so far this winter — the protection was 22 per cent. That’s not spectacular, but when the data were broken down by age groups, the picture was worse. More