Oral Poliovirus Vaccines (OPV)

Health workers give children the oral polio vaccine during the UNICEF-supported immunization campaign in the Community College IDP camp in Marib City, Yemen, in November 2021.

Oral polio vaccines (OPV) are the predominant vaccine used in the fight to eradicate poliomyelitis. There are different oral polio vaccines (tOPV, bOPV, mOPV, OnOPV) that may contain one, a combination of two, or all three different serotypes of an attenuated vaccine.

The attenuated poliovirus(es) contained in OPV is able to replicate effectively in the gut. Still, it is about 10,000 times less able to enter the central nervous system than the wild-type virus. This allows individuals to mount an immune response against the virus. Virtually all countries that have eradicated poliomyelitis have used OPV to interrupt human-to-human transmission of the virus.

To better address the evolving risk of circulating vaccine-derived poliovirus type 2 (cVDPV2), GPEI partners and countries are deploying an innovative tool: the new oral polio vaccine type 2 (nOPV2 ). The vaccine is a modified version of monovalent OPV type 2 (mOPV2), which clinical trials have shown to provide comparable protection against poliovirus while being genetically more stable and less likely to be associated with the emergence of poliovirus. cVDPV2 in low immunity settings.