CDC Predicts Flu Vaccine Will Be More Effective Than Last Year

Last year's vaccine was less effective after a flu strain mutated.

"It was a disappointing year from the point of view of what the vaccine can do," said Dr. William Schaffner, an infectious disease expert at Vanderbilt University and the medical director at the National Foundation for Infectious Diseases.

Last year's flu vaccine against the mutated strain was just 13 percent effective compared to the goal of around 50 to 60 percent effective in other years, CDC director Tom Freiden said at a news conference Thursday.

Health officials are far more optimistic that the vaccine will be more effective this year against multiple strains of the virus that recently affected people in the Southern Hemisphere, Schaffner said.

"A new strain shows up, it continues to be a dominant strain for a few years. We have watched in our summer what has happened in the Southern Hemisphere in their winter," Schaffner explained. "Their dominant strain has been the same, the H3N2 strain."

Depending on which vaccine a person gets, the shot will protect against three or four strains of the virus. Experts pick the strains after consulting a number of factors including flu strains in other parts of the world and past outbreaks of the disease.

"At the moment, we have reasonable confidence that we are going to have a good match between the circulating virus of what’s out there and what’s in the vaccine," Schaffner said.

Every year, 200,000 people are hospitalized from seasonal flu-related complications, according to the CDC.