The polio vaccine protects against polio, a very contagious viral infection that affects the spinal cord and brain. Polio can cause permanent muscle weakness, paralysis, and sometimes death.
Two formulations are available:
The live-virus vaccine is no longer available in the United States because it can mutate to a strain that causes polio in about 1 of every 2.4 million people who receive the vaccine.
The polio vaccine may be combined with other vaccines, such as the diphtheria, tetanus, and pertussis vaccine and sometimes hepatitis B vaccine or Haemophilus influenzae vaccine.
For more information, see the Centers for Disease Control and Prevention's (CDC) Polio vaccine information statement.
(See also Overview of Immunization.)
As a part of routine childhood vaccination, the polio vaccine is given in four doses: at age 2 months, 4 months, 6 to 18 months, and 4 to 6 years.
Because polio is now so rare in the United States, unvaccinated people over 18 years are not given the vaccine unless they are likely to be exposed to the polio virus—for example, if they are traveling to an area where polio is common (see CDC: Travelers' Health), working in a laboratory with materials that may contain the virus, or treating people who may have polio.
If people have a temporary illness, doctors usually wait to give the vaccine until the illness resolves (see also CDC: Who Should NOT Get Vaccinated With These Vaccines?).