This season's flu outbreak has reached the epidemic level, and the Centers for Disease Control and Prevention reports it's expected to get even worse in the coming weeks.
Fifteen children nationwide have died of influenza since the 2014-15 flu season began this fall. The number of people being hospitalized for the flu is also on the rise, with those age 65 and older especially at risk.
The CDC says 22 states are seeing high levels of illness, up from 13 states a week earlier.
And the flu's geographic reach is increasing too, with widespread cases reported in 36 states.
Health officials are encouraging people to get a flu shot even though this year's vaccine formula does not offer as much protection as usual. A prevalent strain of the virus this year, H3N2, mutated enough that it's no longer a close match for the vaccine developed to block it.
CBS News chief medical correspondent Dr. Jon LaPook said that because of this mismatch, the current flu vaccine will probably be about a third less effective than normal.
"In a typical year, the flu vaccine is effective at reducing illnesses caused by the flu by about 60 percent. It's not 100 percent, it's about 60 percent," he explained.
"In previous years when there's been a similar mismatch to what we're seeing this year, the effectiveness goes down to about 40 percent."
However, despite the vaccine's shortcomings, he still urged people to get a flu shot. "Even if it's 40 percent effective, it's better than nothing," LaPook said.
The flu may hit one gender harder than the other.
The CDC recommends a flu shot or nasal vaccine spray every year for almost everyone over the age of six months unless they're allergic.
For those who do come down with the flu, there are now three prescription medications available to help lessen the length and severity of the illness. Antiviral drugs marketed as Tamiflu and Relenza have been on the market for years, and on Dec. 19 the FDA approved another option called Rapivab (peramivir).