This Chicago Tribune graphic, via Talking Points Memo, shows flu vaccination rates by state:

There are exactly two states - South Dakota and Massachusetts - where the majority of citizens have received a flu vaccine. Nevada, meanwhile, has the lowest vaccination rate, coming in at 32.6 percent.

Massachusetts' high vaccination rate may have something to do with the state's universal insurance coverage, which could ease access to vaccinations. South Dakota, meanwhile, appears to have a history of high vaccination rates: It received the Adult Immunization Coverage Award from the CDC in 2012 for achieving the nation's highest flu vaccination rate (neighboring Iowa came in second, trailing by about six percentage points).