Why tackling polio virus 2 resurgence should be priority for India

Aditi Tandon

Tribune News Service

New Delhi, October 2

The government has set up a high-level task force to determine how Wild Polio Virus 2 (WPV2) traces surfaced in the Oral Polio Vaccine (OPV) batches made by Ghaziabad-based Biomed, which is facing criminal prosecution for the lapse.

Since September 2015 when the Global Commission for the Certification of Poliomyelitis Eradication declared the world free of WPV2, the country hasn’t reported WPV2. The last global case of WPV2 was from Aligarh in 1999. Since no case was detected worldwide between 1999 and 2015, the World Health Organisation (WHO) decided to declare the world free of polio virus type 2 in 2015.

It was simultaneously decided that all countries will shift from trivalent oral polio vaccine (containing weakened strains of all three types of wild polio virus 1, 2 and 3) to bilavent OPV (containing strains 1 and 3 only) and totally exclude WPV2 strain from oral vaccines. The reason was that WPV2 use was associated with 90 per cent cases of vaccine derived polio virus worldwide. Post 2015, the WHO asked member states to use only bilavent oral polio vaccines and destroy all forms of WPV2 from cold chains to ensure the world’s WPV2-free status.

Seen in this light, the detection of WPV2 strains in two stool samples from children in UP’s Mirzapur is worrying as it has the potential to impact the world’s WPV2-free status. Health Minister JP Nadda is confident there will be no resurgence of WPV2 and said a probe into the source of contamination of Biomed OPV batches had been launched.

The ministry is flummoxed at how Biomed got WPV2 into its OPV production chain when nationally all existing WPV2 stocks were destroyed by April 2016 as per WHO instructions.

“There is no risk of the disease returning. Our surveillance systems are strong. The WHO is on board and we are proceeding as per WHO protocols. We are alert and will soon determine the cause of contamination. There is no reason to panic,” Nadda said.

But underlying concerns remain because children in Mirzapur and Telangana have received adulterated OPV made by Biomed which was supplying for the government’s routine immunisation plan. WPV2 strains can continue to be discharged into the environment through the oral-fecal route until four months of administration of the OPV containing the type-2 strain.

Ministry officials on Tuesday said children in UP and Telangana would have to be kept under surveillance for four months to completely rule out WPV2 traces from Indian environment. Asked if they are sure WPV2 has not infected children, they said yes.

“Starting 2016 when we shifted to bilavent OPV, we also introduced Inactivated Polio Vaccine (IPV) into our routine immunisation. IPV contains all three polio virus strains and offers newborns immunity to WPV2, which was discontinued in the oral polio vaccines because of its association with vaccine derived polio virus cases,” a top ministry official said.

The government in association with the WHO is conducting heightened surveillance in UP and Telangana to see if there are newborns who have not received IPV. “IPV coverage is being stepped up,” an official said.

Whether India is WPV2-free will only be known after four months when sewage samples from the environment and stool samples of children in Mirzapur and Telangana are tested and cleared.

The ministry, meanwhile, maintains risks of WPV2 continuing in the environment are minimal.