Vaccine-Derived Polio

Aug. 21, 2024

Recently, a vaccine-derived polio case has been confirmed in a two-year-old child from Tikrikilla, Meghalaya. Health authorities clarified that this is not wild poliovirus but an infection seen in individuals with low immunity.

India’s polio-free status: India was declared polio-free by the World Health Organization (WHO) in 2014, with the last wild poliovirus case reported in 2011.
Understanding Vaccine-Derived Polio (VDPV)
- Vaccine composition: The Oral Polio Vaccine (OPV) contains a weakened form of the poliovirus, which stimulates an immune response.
- cVDPV development: On rare occasions, in under-immunized populations, the excreted vaccine virus can circulate, undergo genetic changes, and potentially revert to a form capable of causing paralysis. This is known as circulating vaccine-derived poliovirus (cVDPV).
- Global context: Since 2000, over 10 billion doses of OPV have been administered globally, resulting in 24 cVDPV outbreaks in 21 countries, with fewer than 760 cases.
- Prevention: To stop cVDPV transmission, WHO recommends multiple rounds of high-quality immunisation campaigns.
Key Facts about Polio:
- Polio overview: Polio is a viral infectious disease that can cause irreversible paralysis and even death by affecting the nervous system.
- Wild Poliovirus strains: There are three distinct strains of wild poliovirus:
  - Wild Poliovirus Type 1 (WPV1)
  - Wild Poliovirus Type 2 (WPV2)
  - Wild Poliovirus Type 3 (WPV3)
- Although symptomatically similar, each strain has genetic and virological differences, necessitating separate eradication efforts.
- Transmission: The virus primarily spreads through the fecal-oral route and can multiply in the intestine, where it can invade the nervous system. It predominantly affects children under five.
Available vaccines:
Oral Polio Vaccine (OPV): Administered as a birth dose, followed by three primary doses at 6, 10, and 14 weeks, and a booster dose at 16-24 months.
Injectable Polio Vaccine (IPV): This vaccine is given as an additional dose along with the third DPT (Diphtheria, Pertussis, and Tetanus) vaccine under the Universal Immunization Programme (UIP).