How Effective Is the Flu Vaccine?

The flu vaccine is 70-90 percent effective, depending on the age group and health of the recipient as well as the strain of the flu virus with which he or she comes into contract. The vaccine is most effective in healthy adults and least effective in children, particularly younger children. The vaccine also doesn't work as well in older people, but it still can reduce the effects of the flu and reduces the chance of death from the flu by about 80 percent.

More facts about the flu and the flu vaccine:

• It's best to get the flu vaccine as soon as possible. Although flu season peaks around February, the longer a person waits to get the vaccine, the greater the chance that he or she will get the flu.


• It takes about two weeks for the flu vaccine to take effect. A person can still get the flu if he or she is exposed to the virus during that two-week period.


• The flu virus is constantly changing, so the flu vaccine gets regularly updated, too. The 2010-2011 flu vaccine, for example, was formulated to protect against the 2009 strain of H1N1 as well as two other strains of flu.