At least five days after news of the contamination of polio vaccine by a Ghaziabad-based manufacturer broke, the Union ministry of health and family welfare has said that the risk of any child getting vaccine derived polio disease was “practically” nil. Officials from the ministry, Indian Council of Medical Research (ICMR) and World Health Organization (WHO) were “monitoring” the situation, it said in a statement issued on Wednesday.
The statement came in light of concerns over what this instance of failure of regulation and vaccine contamination could mean for a country that has been “polio-free” since 2014.
Last week, three batches of polio vaccines containing 1.5 lakh vials were reportedly found to be infected with type 2 poliovirus. However, in its statement, the ministry said that only “a few vials” of bivalent oral polio vaccine were found to contain traces of P2 vaccine.
There are three serotypes of poliovirus—Type 1, Type 2 and Type 3—each of which causes poliomyelitis. In India, the last Type 2 wild poliovirus case was detected in 1999.
Until April 2016, children in India were given trivalent oral polio vaccine that contained all three types of poliovirus vaccines (P1, P2 and P3) and provided protection against all three wild polioviruses. Babies born after April 2016, however, were given bivalent OPV, containing only two types of poliovirus vaccines (P1 and P3), because of fears of vaccine derived paralytic polio.
“The decision to switch to Inactivated Poliovirus Vaccine (IPV) and bivalent Oral Polio Vaccine (bOPV) from trivalent Oral Polio Vaccine (tOPV) in all polio campaigns and routine immunisation in India and elsewhere from April 2016 was taken following certification of global eradication of type 2 wild poliovirus. Type 2 component from oral polio vaccine was removed as a part of global polio end game strategy,” the health ministry said in the statement.
Owing to high routine immunisation coverage and the fact that the trivalent OPV was given until 2016, our population level immunity against all three types of virus is very high, according to the ministry.
“This fact was acknowledged and appreciated in recently conducted India Expert Advisory Group on Polio which comprises of international and national experts,” the statement said. “India continues to remain vigilant against all three types of polioviruses.”
Though the ministry has said it is monitoring the situation, experts say that the real effect of this contamination would be seen only in the next six months or so.
“To counter the effect of this contamination, we would now have to administer the IPV [injectable polio vaccine] to each child. However, there is a global shortage of the IPV, which the government would have to contend with now. It would also have to be more stringent now that the strain is out there, and immunity to it is low. The failure of the drug regulatory system in this case also needs to be looked into,” said Dr Vipin M. Vashishtha, former national co-chair, Indian Academy of Paediatrics’ Advisory Committee of Vaccines and Immunization Practices.