If you got a flu shot this year but ended up with the flu anyway, the CDC is explains that scientists make their best guess at what to put in that shot.
This year, two of the three circulating strains are not covered by this year's vaccine. Forty-four states, including Texas, are reporting widespread flu activity.
Researchers say that more than half of all the flu strains identified through lab tests are different from the three that were included this year in the flu shot.
Next Thursday is the day the FDA will discuss what strains will be included in the US vaccine next year.