Vaccine-derived polio (VDP)

Why in news?

Recently, a child from Meghalaya was diagnosed with vaccine-derived polio (VDP).

About:

 VDP occurs when the weakened (attenuated) strain of poliovirus used in the oral polio vaccine (OPV) mutates and regains the ability to cause paralysis.

 VDP typically occurs in areas with low immunisation coverage, poor sanitation, or among immunocompromised individuals.

 More than 90% of VDP outbreaks are due to the Wild poliovirus type 2 (WPV2) present in OPV.

 The Indian government does not count vaccine-associated paralytic poliomyelitis (VAPP) as polio since these cases are sporadic and pose little or no threat to others.

 The WHO declared India polio-free in 2014. This case does not jeopardise India’s polio-free status.

 Types of Poliovirus: WPV1, WPV2, and WPV3 are three types of wild polioviruses (naturally occurring), with identical symptoms but different genetic structures.

o WPV2 and WPV3 were eradicated in 2015 and 2019 respectively with ongoing global efforts to eradicate WPV1.

o Currently, wild poliovirus is endemic in Pakistan and Afghanistan.

 Inactivated Polio Vaccine (IPV) was developed by Jonas Salk using an inactivated virus while Oral Polio Vaccine (OPV) was developed by Albert Sabin, containing a live, attenuated virus.