More about polio
This page provides a link to PATH's work on polio and information about the disease and related vaccines.
On the PATH website
- Poliomyelitis (polio) is a highly infectious disease caused by poliovirus that invades the nervous system and can cause permanent paralysis.
- There are three serotypes of poliovirus (1, 2, and 3). Immunity to one serotype does not protect against the other serotypes.
- Wild poliovirus type 2 has been eradicated and cases of type 1 and 3 combined are less than two hundred cases worldwide.
- Polio can strike at any age but it mainly affects children under age 5.
- The world is very close to eradicating polio. Over 2.5 billion children have been vaccinated since 1988 and the number of polio cases per year is down by 99 percent.
- There are two types of vaccines against polio—a live oral polio vaccine (OPV) delivered as oral drops and inactivated polio vaccine (IPV) delivered via injection.
- OPV is a trivalent vaccine that contains attenuated (weakened) viruses for serotype 1, 2, and 3. The live vaccine viruses can also shed from immunized individuals and circulate as circulating vaccine-derived poliovirus (cVDPV) in a community.
- Among the cVDPV, the serotype 2 cVDPV are the most common with over 90% circulating strains of this serotype. The cVDPV will continue unless global community makes the transition from OPV to IPV after wild poliovirus is eradicated.
- The live attenuated vaccine virus can mutate in some cases, and result in vaccine-associated paralytic polio (VAPP), although this is rare, occurring once for every 2.7 million first doses of the vaccine.
- In most wealthy countries where poliovirus is eradicated, the only vaccine used is IPV. The current price of IPV (>$3/dose) is out of reach for low- and middle-income countries, and they rely mostly on OPV ($.14 -.17/dose) for mass vaccination campaigns.
- In order to accomplish complete global polio eradication and to ensure protection against poliovirus post-eradication, new vaccine and surveillance tools are needed:
- Lower cost OPV for maintaining population immunity, for stamping out pockets of endemic wild poliovirus transmission, and for controlling outbreaks.
- Much more affordable IPV to contain and end VDPVs and sustain population immunity against poliovirus post eradication.
- Affordable IPV-containing pediatric combination vaccines for future birth cohorts in low-income countries.
- Global Polio Eradication Initiative.
- US Centers for Disease Control and Prevention. Polio Vaccination.
- World Health Organization. Immunization, Vaccines, and Biologicals: Poliomyelitis.
- World Health Organization. Poliomyelitis fact sheet.
Page last updated: August 2012.