The strain of the flu that has been most common in the U.S. this season, seasonal influenza A H3N2, is tied to more severe illnesses, hospitalizations and deaths than other flu strains, according to the Centers for Disease Control and Prevention.
Compounding the issue is the fact that about half of the H3N2 viruses this season are "drifted" or different than those included in the flu vaccine this year, making the vaccine less effective.
Tom Frieden, MD, MPH, director of the CDC, warned that this could mean more people will get the flu, thus "crowding emergency departments and hospitals."
Dr. Frieden and the CDC are urging everyone to get vaccinated. "We can save lives with a three-pronged effort to fight the flu: vaccination, prompt treatment for people at high risk of complications, and preventive health measures."
H3N2 flu viruses have been the dominate strain of flu virus in flu seasons past, including the 2012-13, 2007-08 and 2003-04 seasons.