Global spread of vaccine-derived polio disease (VDPD) still a high risk: World Health Organization.

• The risk of global spread of poliovirus remains a public health emergency of international concern, a World Health Organization committee has found after looking into updates from 10 countries.
• While the risk of global spread of wild poliovirus remains, the risk of circulating vaccine-derived ones is higher.
• Several measures like declaring poliovirus transmission as a national public health emergency and ensuring vaccinations for travellers and residents have been recommended by WHO.

About Polio

• Poliomyelitis (polio) is a highly infectious disease that invades the nervous system.
• There are 3 types of wild polio virus – type 1, type 2, and type 3. Only type 1 wild poliovirus remains in circulation.
• There are two types of vaccinations that work against poliovirus: inactivated poliovirus (IPV) and oral poliovirus (OPV).

1. IPV is produced from wild-type poliovirus strains that have been inactivated (killed) with formalin.
2. OPV contains an attenuated (weakened) vaccine-virus, which activates an immune response in the body.

• However, OPV can lead to rare emergence of VDPVs when there is prolonged circulation or replication of the vaccine virus.

Types of VDPVs:

• Circulating VDPV (cVDPV), immunodeficiency VDPV (iVDPV), and ambiguous VDPV (aVDPV).
• VDPVs are mostly found in children with immune-deficiency and among populations with low immunity levels.
• In 2014, India was officially declared polio-free, along with the rest of the South-East Asia Region.