CDC Flu Report: Vaccine has a 23 Percent Effectiveness Rate

The U.S. Centers for Disease Control and Prevention (CDC) calculated the flu vaccine's effectiveness rate this year and discovered that due to a mismatch in the flu strains, the vaccine is only 23 percent effective.

Health officials reported that the predominant flu virus influenza A (H3N2) that was predicted last year, had changed after the vaccine was already mass produced and distributed. Since the strain has changed genetically, the vaccine is no longer as effective as the experts believed.

The report added that the effectiveness rate varies based on people's age. The rate was the highest in children between the ages of six months and 17 years at 26 percent. In people between the ages of 18 and 49, the effectiveness rate was 12 percent. In older people aged 50 and above, the rate fell down to 14 percent.

"These estimates of vaccine efficacy are doleful, and they are entirely consistent with what the CDC told us they were likely to be based on the studies in the lab," said Dr. William Schaffner, an infectious disease expert at Vanderbilt University Medical Center in Nashville, reported by Reuters.

CDC epidemiologist Brendan Flannery added, "There are some years when the virus drifts and the vaccine still provides pretty good protection. This is not one of those years."

Despite the low effectiveness rate, the agency still recommends people to get the flu shot. The shot can protect against other strains that might circulate later on during the season.

The CDC has done flu vaccine studies for about 10 years. Overall effectiveness rates have ranged from 10 percent to 60 percent.