This year’s flu shot is doing a fairly average job of protecting people against the pervasive winter virus, according to the annual interim effectiveness report released Thursday by the U.S. Centers for Disease Control and Prevention.The agency said the shot has been 45% effective overall and 55% effective in children. The vaccine was less effective for influenza A than B and did considerably worse among 18- to 49-year-olds, where it was only 25% effective. Against one type of influenza A, H1N1, it had no proven effectiveness in younger adults. Previous seasons have ranged from 40% to 60% effe...
