Poliomyelitis, or polio, is a contagious disease caused by a virus that affects the nervous system. The virus enters the body through the mouth and replicates in the gastrointestinal tract and lymphoid tissue before entering the bloodstream. In a small number of cases it enters the central nervous system where it can cause severe neurological disease. Approximately 95% of persons infected with polio will have no symptoms. However, approximately 4-8% of infected persons have minor symptoms, such as fever, fatigue, nausea, headache, flu-like symptoms, stiffness in the neck and back, and pain in the limbs, which often resolve completely. Fewer than 1% of polio cases result in permanent paralysis of the limbs (usually the legs). Of those paralyzed, 5-10% die when the paralysis strikes the respiratory muscles. The death rate increases with increasing age.
The CDC recommends inactivated polio vaccine (IPV) for the prevention of polio. Children should receive 3 primary doses of IPV at: 2, 4, and 6-18 months of age. A booster dose should be given at 4-6 years of age. Routine vaccination of adults (18 years of age and older) who reside in the United States is not necessary or recommended because most adults are already immune and have a very small risk of exposure to wild poliovirus in the United States. However, adults who have never been vaccinated against polio and are in a high risk category (i.e. selected laboratory workers, travelers to areas where poliomyelitis is endemic, and healthcare personnel in close contact with patients who may be excreting wild polioviruses) should get 3 doses of IPV: the first dose at any time, the second dose 1 to 2 months later, and the third dose 6 to 12 months after the second. Adults in the high risk categories who have had 1 or 2 doses of polio vaccine in the past should get the remaining 1 or 2 doses. It doesn’t matter how long it has been since the earlier dose(s).