The Centers for Disease Control and Prevention says now is the time to prepare for the flu season, which normally begins around this time of year.
The CDC says last year's flu shot was 13 percent effective. Normally, the vaccine is 50 to 60 percent effective.
"So far what we've seen in the Southern hemisphere and over the summer in the U.S. suggests that this years' vaccine should be a good match against this years' circulating influenza, but only time will tell for sure," said CDC Director Dr. Tom Frieden.
Flu vaccinations are now arriving at pharmacies, public health department centers and doctors' offices.