The flu vaccine is less effective this year because the virus has mutated, the CDC warned in an official health advisory this week.CNN reports that of the H3N2 virus samples  (this year’s most predominant flu strain) collected from October 1 through November 22 this year, 58% different from the H3N2 virus included in this year’s shot. Which means this particular flu strain has mutated or “drifted” significantly since the vaccination was developed pre-flu season.”In past seasons during which predominant circulating influenza viruses have been antigenically drifted [mutated], decreased vaccine effectiveness has been observed,” the CDC report said. “However, vaccination has been found to provide some protection against drifted viruses.”In English: If you get the shot, there’s a good chance you could still get the flu, but your chance of it being extremely severe will be lower. The shot will also protect you against the original, non-muted strains out there — which can’t hurt.This means, more than ever, it’s important to be smart to dodge sickness this flu season. For some help, here’s four more simple ways to fend off flu.More Articles on Influenza:Are You Falling for These Flu Vaccine Myths?The Flu Vaccine’s Powers—and Limitations