What is the influenza vaccine?
Two types of influenza vaccine are now available. Inactivated (killed) influenza vaccine, given as a shot, has been used in the United States for many years. A live, weakened vaccine was licensed in 2003. It is sprayed into the nostrils. Influenza viruses change often. Therefore, influenza vaccine is updated every year. Protection develops about 2 weeks after getting the shot and may last up to a year. Some people who get flu vaccine may still get flu, but they will usually get a milder case than those who did not get the shot. Flu vaccine may be given at the same time as other vaccines, including pneumococcal vaccine. Some inactivated flu vaccine contains thimerosal, a form of mercury, as a preservative. Some contains only a trace of thimerosal. There is no scientific evidence that thimerosal in vaccines is harmful, and the known benefits of the vaccine outweigh any potential risk from thimerosal. If you have questions about thimerosal or reduced-thimerosal flu vaccine, ask your doctor.
