"Each year since 2004 and 2005, the Centers for Disease Control and Prevention in Atlanta estimated the effectiveness of the seasonal influenza vaccine," Dr. Thomas Frieden told reporters in a telephone news conference. "We look at how likely that vaccine is to keep you out of a doctor's office. We have also looked at how likely it is to prevent people from being hospitalized for dying from the flu and those numbers tend to be similar or perhaps a little more effective at preventing hospitalization or death."
The study subjects were tracked from Dec. 3, 2012, to Jan. 2.
"Once we looked at the differences across study sites and corrected for that but not other factors, we found the overall vaccine effectiveness to be 62 percent -- typical of most years. That means that if you got vaccinated you were about 60 percent less likely to get the flu that required you to go to your doctor," Frieden said. "So what we have known for a long time is that the flu vaccine is far from perfect. But it's still by far the best tool we have to prevent the flu. Now, there are differences in different groups. In the past we've found for example that younger people tend to be better protected by the vaccine than older people."
The seasonal flu vaccination is far from perfect, but it's by far the best tool we have to prevent influenza, Frieden said.
The seasonal flu vaccine is less effective on those who are frail, elderly, people who might have had cancer, chemotherapy, people who may have immune systems that are weakened or be on medications that would weaken their immune system, including long-term oral treatments, Frieden said.
"It's kind of the opposite of what we'd wish. The people who are most susceptible to severe influenza are also less likely to get the benefit that others get from the vaccine," Frieden said.
"Childhood vaccines get more than 90 percent vaccine efficacy. That's what we'd like to see."
New York Gov. Andrew Cuomo Saturday declared a public health emergency for the entire state in response to the increasingly severe flu season, and urged all New Yorkers to get a flu shot.