(AP) It turns out that this year's flu shot is doing a startlingly dismal job of protecting senior citizens, the most vulnerable age group.
The vaccine is proving only 9 percent effective in people 65 and older against the harsh strain of the flu that is predominant this season, the Centers for Disease Control and Prevention said Thursday.
Health officials are baffled as to why this is so. But the findings help explain why so many older people have been hospitalized with the flu this year.
Advertisement - story continues below