VACCINE-DERIVED POLIO INFECTION (Syllabus: GS Paper 3 – Sci and Tech)

Context: Meghalaya's Health Minister announced that the World Health Organization (WHO) is investigating whether a new strain of polio has affected a two-year-old child from Tikrikilla.

Vaccine-Derived Polio Infection

• About: It is a strain related to the weakened form of the virus used in oral polio drops for immunisation.
• Safety and Efficacy: The vaccine is generally safe and has been instrumental in eradicating polio in most countries.
• Risks: In rare cases, the vaccine can trigger polio in children with weakened immune systems.
• Immune Response: The vaccine activates an immune response, and the vaccine-virus can be excreted and change genetically in the bloodstream over time.
• Circulation and Transmission: The vaccine-derived virus can continue circulating among children, regaining the ability to transmit and cause severe infection.
• Chronic Infection: The vaccine virus can cause chronic infection in children with weakened immune systems, replicating in their gut and potentially gaining the ability to cause severe disease.
• Last Case in India: India’s last case of wild poliovirus — infection caused by the naturally occurring virus was detected in West Bengal’s Howrah district in 2011.
• India’s Polio Status: After successfully preventing any wild polio infections for three years, the country was declared polio-free in 2014.

o India continues to be polio-free unless cases of wild polio virus infection are detected.

• Types of Polio Virus: Wild poliovirus type 1, 2 and 3 (WPV1, WPV2 and WPV3).

o There are three types of polio virus that cause infections in humans. The weakened forms of all these viruses were included in the oral polio vaccine.