The Centers for Disease Control and Prevention (CDC) issued a Health Alert Network advisory last week stating that approximately half of the H3N2 viruses detected so far are different, mutated strains from the ones included in this year’s vaccine, which means flu shots could be less effective.

Despite the warning, the CDC says people should get the vaccine. “We are recommending strongly that people who haven’t been vaccinated get vaccinated. Every year vaccine is the best way to protect yourself against the flu,” said Joseph Brusee, M.D., chief of the Flu Epidemiology and Prevention branch at CDC.

The CDC is asking healthcare providers to encourage all patients six months and older who have not yet received a flu vaccine this season to be vaccinated. There are several flu vaccine options for the 2014-15 flu season. Clinicians should also encourage patients with a high risk for flu complications—the young, elderly and people with chronic diseases—to seek care promptly to determine if treatment with flu antiviral medications is warranted.

In addition, the agency stated, antiviral treatment should be started as soon as possible after illness onset, ideally within 48 hours of the start of symptoms. However, antiviral treatment might still have some benefits in patients with severe, complicated or progressive illness and in hospitalized patients when started after 48 hours.

The CDC also recommends preventive health practices for patients, such as staying home when sick, hand washing and covering their mouth when coughing.