India continues to remain vigilant against all three types of polioviruses, the WHO and UNICEF have said in a joint statement.
The reassurance from the global bodies comes in the wake of the recent controversy over the contamination of Oral Polio Vaccine (OPV) and consequently, fears of a possible outbreak of vaccine derived polio-virus. However, due to the fact that India has achieved high coverage of routine immunisation, the risk of children getting vaccine derived poliovirus is "minimal", the WHO has said.
According to the global bodies, a team from the Indian Council of Medical Research, Drug Controller General of India and the Union Ministry of Health and Family Welfare has investigated the matter after the presence of Type 2 polio vaccine virus was detected in some sewage and stool samples. The investigation revealed that a "few" vials of bivalent OPV, supplied by a Ghaziabad-based manufacturer had traces of Type 2 polio vaccine virus (there are three serotypes of poliovirus—Type 1, Type 2 and Type 3—each of which can cause poliomyelitis).
However, the trivalent vaccine, containing Type 2 poliovirus, has been phased out across the world. In April 2016, it was phased out as a part of the polio endgame strategy.
Post April 2016, the bivalent oral polio vaccine (bOPV) has replaced the trivalent OPV (tOPV) in all polio campaigns and routine immunisation in India.
With reference to the recent crisis, and the fears of a possible outbreak, the WHO has said that the Union health ministry has taken "immediate and decisive action" by withdrawing the vaccine supplied by the manufacturer from all states. "Despite the risk of vaccine derived polio being minimal, the immediate withdrawal of these vaccines demonstrates the commitment of the government to the health of children," the statement said.
The last polio case due to wild poliovirus in the country was detected on January 13, 2011.