For more information, see the Polio vaccine information statement.
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. One contains killed virus and is injected. The other contains live, weakened virus and is taken by mouth. The live-virus vaccine is no longer available in the United States because it causes polio in about 1 of every 2.4 million people who receive the vaccine.
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 Travel Health Advice), working in a laboratory with materials that may contain the virus, or treating people who may have polio.