Protecting against polio -R Prasad
Why the inactivated polio vaccine is essential for India
With wild polio virus strains reduced by 99.9% since 1988, the world is inching towards eradicating polio. But unfortunately, more children today are affected by the live, weakened virus contained in the oral polio vaccine (OPV) that is meant to protect them. The weakened virus in the vaccine can circulate in the environment, occasionally turn neurovirulent and cause vaccine-derived poliovirus (VDPV) in unprotected children. While the wild-type virus has caused 22 and 25 polio cases in 2017 and 2018 (as on October 30, 2018), respectively, in just two countries (Pakistan and Afghanistan), VDPV was responsible for 96 and 75 polio cases in more countries during the same periods. “Paradoxically, vaccination (using OPV) has become the main source of polio paralysis in the world,” notes a 2018 paper in The Lancet.
The VAPP burden
While circulating VDPV strains are tracked, and outbreaks and cases are recorded and shared, little is known about vaccine-associated paralytic poliomyelitis (VAPP) cases, particularly in India. VAPP occurs when the virus turns virulent within the body of a recently vaccinated child and causes polio. The frequency of VAPP cases varies across countries. With high-income countries switching to the inactivated polio vaccine (IPV) that uses dead virus to immunise children, the VAPP burden is concentrated in low-income countries which continue to use the OPV.
In spite of the World Health Organisation asking all countries using the OPV to include a “continuous and effective system of surveillance” to monitor the frequency of VAPP in 1982, India did not comply. Data on VAPP became available only years after active polio surveillance was initiated in 1997, say Jacob John, a virologist and formerly with the Christian Medical College, Vellore, and a polio expert, and Dhanya Dharmapalan in a paper published in September in the Indian Journal of Medical Ethics. However, even after 1997, India did not count VAPP cases. “This is because it does not add value to the polio elimination programme,” says Pradeep Haldar, Deputy Commissioner of the Immunisation Division, Ministry of Health and Family Welfare.
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