There are hundreds of strains of the flu virus, and it's impossible to vaccinate against all of them. Each year scientists select the strains that in their opinion pose the largest danger over the coming 12 months, and a new vaccine is targeted against those specific strains. Manufacturing millions of doses of vaccine takes months. Even if the scientists discover that their selections were incorrect before anyone is inoculated, it's too late to change the formula.
And that's what happened this year. There's a transcript of a CDC press briefing in December that explains everything, and you don't an M.D. or Ph.D. to understand it. Most of the flu epidemic at present is caused by a variant of H3N2, but it's a different H3N2 from what the vaccine was designed to combat. There is speculation that those who received the vaccine and then caught H3N2 aren't getting as sick as those who didn't get the vaccine, if that's any consolation.
I believe the scientists are doing the best they can. It's been at least five years and more likely ten years since I contracted a bad case of the flu. That's not a bad average. And we've come a long way since the 1976 swine flu fiasco.
