Cases of the flu are already on the rise across the U.S., and health officials warn the worst is yet to come, reports NBCNews.com. The Centers for Disease Control and Prevention reports that symptoms associated with the seasonal virus are currently widespread in 36 states across the country. Lab tests have shown that the dominant virus in circulation is the H3N2 influenza strain, which tends to cause more severe illness than other strains. And new research has shown that the main process for manufacturing the flu vaccine triggers mutations in H3N2 that render the antibody stimulant less effective. “The mutation just happened to be in a very bad spot on the virus to make it essentially be a mismatch for the vaccine,” explains Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases. This combination of factors doesn’t bode well for the flu season in the coming months; the vaccine may prevent only about 10 percent of infections. But health officials are still urging Americans to get a flu shot, arguing that some protection is better than none.