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Rare Polio Case in Meghalaya
Context:
The discovery of a two-year-old child in Meghalaya testing positive for polio—a infectious viral disease—has caused concern. However, the Health Ministry officials confirmed that the case is vaccine-derived and reassured that it does not threaten India’s polio-free status.
Vaccine-Derived Polio Infection (VDPV)
- VDPV is a strain related to the weakened poliovirus used in the oral polio vaccine (OPV).
- If this weakened virus circulates in populations with inadequate or no vaccination or replicates in someone with an immunodeficiency, it can revert to a form that causes illness and paralysis.
- While the vaccine is generally safe and has led to the eradication of polio in many countries, it can occasionally cause the disease in children with weakened immune systems.
- The vaccine-virus, while stimulating an immune response, can be excreted and, over time, undergo genetic changes in the bloodstream.
- OPV can result in vaccine-derived polio strains if the weakened virus spreads among children, progressively regaining its capacity to transmit rapidly and cause severe infections.
Vaccine-Derived Polio Cases Before
- India’s last case of wild poliovirus, caused by the naturally occurring virus, was reported in 2011 in West Bengal’s Howrah district.
- After successfully avoiding any wild polio infections for three years, the country was declared polio-free in 2014.
- However, vaccine-derived polio cases have been reported since then.
- In 2013, an 11-month-old child with a weakened immune system in Maharashtra’s Beed district died from vaccine-derived polio.
- Additionally, a 2.5-year-old child in Delhi was affected, and vaccine-derived poliovirus was found in sewage samples in Kolkata in 2022.
- India continues to be polio-free unless cases of wild poliovirus infection are detected.
Since 1988, wild poliovirus cases have dropped by over 99%, from an estimated 350,000 cases across more than 125 endemic countries to just 6 reported cases in 2021.
Among the three wild poliovirus strains (types 1, 2, and 3), type 2 was eradicated in 1999, and type 3 was eradicated in 2020. As of 2022, wild poliovirus type 1 remains endemic only in Pakistan and Afghanistan.
