Scottsdale, Arizona - Have you had your flu shot? The time is now, according to the Centers for Disease Control and Prevention (CDC).  "The most important way that we can prevent influenza infection is to get vaccinated," says Dr. Nipunie Rajapakse, a Mayo Clinic pediatric infectious diseases specialist. "We recommend influenza vaccine for everyone over 6 months of age, and we would really encourage people to get their vaccines as soon as the vaccines come out."

It's important to get vaccinated each year, because the influenza virus evolves quickly, and last year's vaccine may not protect you from this year's virus. Traditional vaccines called trivalent vaccines are created to protect against three flu viruses: an influenza A (H1N1) virus, influenza A (H3N2) virus, and influenza B virus. There are also quadrivalent vaccines created to fight against the same trivalent viruses plus an additional B virus.

"Though each influenza season can be quite unpredictable, based on the bad flu season seen in Australia earlier this year, there is concern that this may be a very severe flu season in the U.S. as well," says Dr. Rajapakse. "People should do everything they can to protect themselves and their families including getting vaccinated, washing their hands often, and staying home from work and school if they do get sick."

The CDC recommends everyone age 6 months and older be given an injectable flu vaccine by the end of October if possible. It takes up to two weeks to build up immunity after a flu shot.