This year's vaccine will target the same strain of the virus, the H3N2 strain, that mutated last year, leaving the vaccine less effective, officials at the U.S. Centers for Disease Control and Prevention and the National Foundation for Infectious Diseases announced Thursday.
"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.
The CDC reported that the rate of flu-related hospitalizations during the last flu season among those over the age of 65 was the highest since records began about 10 years ago. Additionally there were 145 pediatric flu deaths, according to the CDC.
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.
“Vaccination is the single most important step people can take to protect themselves from influenza,” Frieden said. “Flu can be serious and it kills tens of thousands of Americans each year. Vaccination is easier and more convenient than ever, so get yourself and your family protected.”