Oral polio vaccine (OPV) cessation
Once wild poliovirus transmission has been stopped globally, the attenuated viruses present in oral polio vaccine (OPV) will be the only source of live polioviruses in the community. These vaccine-viruses would continue to cause vaccine-associated paralytic poliomyelitis (VAPP) and polio outbreaks due to circulating vaccine-derived polioviruses (cVDPVs). In the post-eradication era therefore, use of the oral polio vaccine in routine immunization programmes will need to be phased out to eliminate these risks.
|
“After eradication of wild poliovirus, continued used of oral polio vaccine (OPV) would compromise the goal of a polio-free world.”
Advisory Committee on Poliomyelitis Eradication, 2004
|
There are three reasons for eventually stopping use of oral polio vaccine for routine immunization.
Polio cases due to vaccine-associated paralytic poliomyelitis (VAPP)
Despite the safety and effectiveness of OPV, the live attenuated vaccine virus can cause vaccine-associated paralytic poliomyelitis (VAPP). VAPP is very rare and occurs in an estimated one in 2.7 million children receiving their first dose of oral polio vaccine.
While the public health benefits of OPV continue to outweigh the VAPP risk in most countries, this balance will change when wild poliovirus transmission is interrupted globally. Continued use of OPV is predicted to result in several hundred new VAPP cases worldwide every year.
Polio outbreaks due to circulating vaccine-derived poliovirus (cVDPV)
On very rare occasions, if a population is seriously under-immunized, there are enough susceptible children for the excreted vaccine-derived polioviruses to begin circulating in the community. These viruses are called circulating vaccine-derived polioviruses (cVDPV) and can cause outbreaks and paralysis.
Polio outbreaks due to immunodeficiency-related vaccine-derived poliovirus (iVDPV)
Continued use of OPV would, rarely, lead to prolonged excretion (>6 months) of vaccine-derived poliovirus from people with severe primary immunodeficiency syndromes. These iVDPVs are capable of infecting other people and could theoretically reintroduce poliovirus into the general population.