There's at least one strain of the flu virus going around that can't be treated with the common flu shot. Health officials say the vaccine usually treats at least three strains of the virus but one of them has mutated. That means people who've already gotten a flu shot could still get sick with the H3N2 strain of the flu. But that doesn't mean the vaccine doesn't work. Officials say it will still ward off some strains of H3N2 and at least two other strains of the flu.
