Poliovirus is a member of the enterovirus subgroup, family Picornaviridae. There are three poliovirus serotypes (P1, P2, and P3). Immunity to one serotype does not produce significant immunity to the other serotypes.

Polio, or poliomyelitis, is a highly infectious viral disease, which mainly affects young children.  Poliovirus is spread person-to-person via fecal-oral route, and less frequently, via oral-oral route. The virus enters through the mouth, and primary multiplication of the virus occurs at the site of implantation in the pharynx and gastrointestinal tract. The virus is usually present in the throat and in the stool before the onset of illness. One week after onset, there is less virus in the throat, but virus continues to be excreted in the stool for several weeks. The virus invades local lymphoid tissue, enters the bloodstream, and then may infect cells of the central nervous system. Replication of poliovirus in motor neurons of the anterior horn and brain stem results in cell destruction and causes the typical manifestations of poliomyelitis.

Most people infected with poliovirus are asymptomatic. When symptoms are present, they usually last less than a week and may include influenza-like illness, upper respiratory tract infection, and/or gastrointestinal disturbances.  In a very small proportion of cases in children (<1%), the disease causes paralysis, which can be permanent, and even lead to death.

Persons infected with poliovirus are most infectious from 7 to 10 days before and after the onset of symptoms, but poliovirus may be present in the stool for 3 to 6 weeks after acute infection.  It can be transmitted even if the infected person is asymptomatic.

There is no cure for polio.  Treatment is symptomatic.  Polio can only be prevented by immunization. There are two types of vaccine that can prevent polio: inactivated poliovirus vaccine (IPV) and oral poliovirus vaccine (OPV).  Since 2000, in the United States, only Inactivated Poliovirus Vaccine Inactivated, trade name, IPOL® has been available. 

IPV is indicated for active immunization of infants, children, and adults for the prevention of poliomyelitis caused by poliovirus serotypes P1, P2, and P3. A primary series of IPV consists of three doses with routine administration recommendations at ages 2 months, 4 months, and 6-18 months. A booster dose is recommended between 4-6 years of age.

There are three combination pediatric vaccines that contain inactivated polio vaccine available in the United States – KINRIX, PEDIARIX, and Pentacel®.