WILD POLIO VIRUS TYPE 2 ERADICATED
There are three types of wild poliovirus (WPV) - type 1, type 2 and type 3. In 1999, the last case of type 2 was eradicated. Since then, zero cases of type 2 polio have occured.
OPV 2 CESSATION
OPV contains attenuated (weakened) polioviruses. Even though the viruses have been transformed to a form in which they cannot cause polio, once eradication of wild polioviruses occurs OPV will be discontinued. , the oral polioviruses vaccine must be discontinued. Because type 2 polio has been eradicated since 1999, vaccination against wild poliovirus type 2 is no longer necessary.
The oral polio vaccine (OPV) contains a live, attenuated (weakened) vaccine-virus. When a child is vaccinated, the weakened vaccine-virus replicates in the intestine and enters into the bloodstream, triggering a protective immune response in the child. Like wild poliovirus, the child excretes the vaccine-virus for a period of six to eight weeks. Importantly, as it is excreted, some of the vaccine-virus may no longer be the same as the original vaccine-virus as it has genetically altered during replication. This is called a vaccine-derived poliovirus. In rare circumstance, VDPVs can cause an outbreak. These rare outbreaks occur when a vaccine-related virus is passed from person-to-person, mutating along the way and acquiring the wild virus transmissibility and neurovirulence characteristics. Almost all cVDPV outbreaks in recent years have been caused by a type 2 vaccine-derived virus.
Although wild polio virus type 2 was eradicated globally in 1999, vaccine-related type 2 viruses continue to cause the majority of cVDPV outbreaks and cases and many VAPP cases. The WHO Strategic Advisory Group of Experts on immunization (SAGE) has therefore called for a global, coordinated withdrawal of the type 2 component of trivalent OPV from routine immunization programmes in 2016. For countries which use only OPV in their routine immunization programmes, this will require switching from trivalent OPV to bivalent OPV (type 1 and 3) for that purpose.
There are three types of wild poliovirus (WPV) - type 1, type 2 and type 3. In 1999, the last case of type 2 was eradicated. Since then, zero cases of type 2 polio have occured.
OPV 2 CESSATION
OPV contains attenuated (weakened) polioviruses. Even though the viruses have been transformed to a form in which they cannot cause polio, once eradication of wild polioviruses occurs OPV will be discontinued. , the oral polioviruses vaccine must be discontinued. Because type 2 polio has been eradicated since 1999, vaccination against wild poliovirus type 2 is no longer necessary.
The oral polio vaccine (OPV) contains a live, attenuated (weakened) vaccine-virus. When a child is vaccinated, the weakened vaccine-virus replicates in the intestine and enters into the bloodstream, triggering a protective immune response in the child. Like wild poliovirus, the child excretes the vaccine-virus for a period of six to eight weeks. Importantly, as it is excreted, some of the vaccine-virus may no longer be the same as the original vaccine-virus as it has genetically altered during replication. This is called a vaccine-derived poliovirus. In rare circumstance, VDPVs can cause an outbreak. These rare outbreaks occur when a vaccine-related virus is passed from person-to-person, mutating along the way and acquiring the wild virus transmissibility and neurovirulence characteristics. Almost all cVDPV outbreaks in recent years have been caused by a type 2 vaccine-derived virus.
Although wild polio virus type 2 was eradicated globally in 1999, vaccine-related type 2 viruses continue to cause the majority of cVDPV outbreaks and cases and many VAPP cases. The WHO Strategic Advisory Group of Experts on immunization (SAGE) has therefore called for a global, coordinated withdrawal of the type 2 component of trivalent OPV from routine immunization programmes in 2016. For countries which use only OPV in their routine immunization programmes, this will require switching from trivalent OPV to bivalent OPV (type 1 and 3) for that purpose.