Global spread of vaccine-derived polio still a high risk : WHO

Global spread of vaccine-derived polio still a high risk : WHO

According to the recent World Health Organization (WHO), the risk of global spread of vaccine-borne polio is still very high.

A WHO committee has studied updates provided by several countries.

Following this study, the Committee stated that while the risk of global spread of wild poliovirus remains, the risk of global spread of vaccine-derived poliovirus (VDPV) is highest.

Poliomyelitis (polio) is a highly infectious disease that affects the nervous system. There are 3 types of wild polio virus – Type-1, Type-2 and Type-3.

Currently only type-1 wild poliovirus is being transmitted.

Two types of vaccines are given against the polio virus:

  • Inactivated Polio Vaccine (IPV), and Oral Polio Vaccine (OPV)
  • IPV is produced from the wild type poliovirus strain. These are inactivated (killed) with formalin.
  • OPV is made from an attenuated (weakened) virus. It activates the immunity in the body.
  • However, in extremely rare circumstances OPVs can also cause vaccine-borne polioviruses (VDPVs).
  • This happens when the vaccine-polio virus continues to circulate for a long time or new copies of the virus keep forming.

The types of VDPVs are:

  • Immunodeficiency vaccine-associated poliovirus (iVDPV), and ambiguous vaccine-associated poliovirus (aVDPV).
  • VDPVs are mostly found in children who have a weak immune system. In addition, this virus also infects such a section of the population, which has a very weak level of immunity.
  • In 2014, India along with the rest of the South-East Asia region was officially declared polio-free.

Source – Down to Earth

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