Polio-free status intact, says WHO

Strain found in sewage recently sparks fear

 As many as 15 samples of vaccine-derived polio virus (VDPV) were found in India in the last one-and-half years, but none of them led to polio infection in a child.

The World Health Organisation on Saturday allayed apprehensions about a polio scare. “In India, between Jan 2015 and May 2016, a total of 15 sewage samples collected from different parts of the country tested positive for VDPVs. However, no children have been found to be affected by these VDPVs,” a WHO official told DH.

The discovery of a VDPV (type-2) from a sewage sample near Secundrabad railway station triggered a public health scare. Reporting of an Acute Flaccid Paralysis case from Uttar Pradesh within days compounded the scare of the return of the crippling infection.
The south-east Asia region was certified polio-free on March 27, 2014 and there is no threat to the region’s polio-free status from the VDPV isolates in the sewage samples, said the WHO.

Vaccine-derived polio cases are rare but known risks associated with oral polio vaccine campaign that India pursued for more than two decades.

As India remains polio free since 2011, strict environmental surveillance, collection of samples from sewage, is being conducted regularly from 30 sites across seven states in India to check the VDPV cases, if any.

Most cases of VDPV polio are caused by the type 2 polio virus, which was eradicated from the wild in 1999. But the trivalent oral polio vaccine being administered in the pulse polio campaign carry live but weakened forms of all the three types of polio virus (type 1, 2 and 3) to protect the kids.

As a part of the polio endgame strategy India along with other polio-endemic nations switched from trivalent to bivalent OPV (which does not carry type 2 polio virus) from April 2016 so that the type 2 immunity will be maintained. In addition, there would be a single dose of inactivated polio vaccine injection.

“VDPVs are a risk to a global polio-free world. The essential part of the polio endgame strategy is to begin phasing out the OPV strains (starting with the type 2 component) to eventually eliminate the risk of VDPVs altogether,” pointed out another WHO official.