Polio Disease and Poliovirus Containment
Poliovirus containment is focused on eradicated polioviruses. Wild poliovirus type 2 (WPV2) and wild poliovirus type 3 (WPV3) were declared eradicated in 2015 and 2019, respectively. Containment measures are in place for laboratories and other facilities that handle or store eradicated polioviruses.
There are three types of wild poliovirus (WPV): type 1, type 2, and type 3. People must protect themselves against all three types of the virus to prevent polio disease. Polio vaccination is the best protection.
Type 2 wild poliovirus was declared eradicated in September 2015. The last detection was in India, 1999. Type 3 wild poliovirus was declared eradicated in October 2019. It was last detected in November 2012. Only type 1 wild poliovirus remains.
There are two vaccines used to protect against polio disease: oral polio vaccine and inactivated poliovirus vaccine. For more information see OPV Cessation – GPEI (polioeradication.org).
The oral poliovirus vaccine (OPV) is used in many countries to protect against polio disease. Oral poliovirus vaccine contains attenuated or weakened version of either one (monovalent OPV), two (bivalent OPV), or all three (trivalent OPV) poliovirus types.
After wild poliovirus type 2 was declared eradicated in 2015, the world switched from trivalent OPV to bivalent OPV. Bivalent OPV contains poliovirus type 1 and 3. This switch means that the bOPV used globally no longer protects against WPV2. Countries that use bOPV for routine immunization have added a single dose of IPV to protect against WPV2.
In rare instances, the vaccine-virus may be able to circulate over time and mutate in communities with insufficient immunity or immunocompromised individuals. These mutated OPV strains can cause polio disease. They are called vaccine-derived polioviruses (VDPVs).
For more information on polio vaccination see Polio Vaccination | CDC.
IPV protects people against all three types of poliovirus. IPV does not contain live virus and cannot cause disease. It protects people from polio disease but does not stop transmission of the virus.
OPV can be used to contain a polio outbreak. Use of all OPV will stop when polio is eradicated globally. This will prevent re-establishment of transmission from VDPVs. For more information on polio vaccination see Polio Vaccination | CDC.