Even as the health ministry and the World Health Organisation (WHO) have stepped up efforts to enhance surveillance particularly in UP, Maharashtra and Telangana where the contaminated type 2 polio virus vaccine was administered in children, experts say contaminated polio vaccine batches in circulation is not a threat to government’s polio immune strategy.
Around 1.5 lakh oral polio vaccine (OPV) vials which were found to be contaminated by Type 2 poliovirus were manufactured by Ghaziabad based Biomed. This was done despite, government having ordered the manufacturers to take measures for complete destruction of Type 2 poliovirus by April 25, 2016. The health ministry has, however, directed the company to stop the distribution, sale and manufacturing of the vaccine till further orders.
Says Dr Pramod Jog, former president, Indian Academy of Paediatrics (IAP), “Type 2 polio virus vaccine which has been administered is vaccine derived and therefore is not an infectious one. Besides this, it has not mutated to the extent that will allow poliomyelitis to make a comeback.”
As part of the national immunisation programme, government had started giving injectable polio vaccine (IPV) along with bi-valent oral polio vaccine (OPV) from April 25, 2016 onwards to build population immunity in India for complete polio eradication.
“There is no need to panic. The immunization against polio should continue as per the IAP Immunization schedule. Both vaccines, IPV and bi-valent OPV are safe and their use should be continued. IAP supports national immunization programme and the efforts for eradication of poliomyelitis,” Dr Jog adds.
Government’s polio immune strategy is aimed to make a switch over from trivalent OPV to bivalent OPV in a phased manner to completely stop OPV and switch to IPV by 2020.
The trivalent OPV that was used till April 2016 contained three types of poliovirus vaccines (P1, P2 and P3) and protected against all three types of wild polioviruses – type 1, type 2 and type 3, while bivalent OPV contains two types of poliovirus vaccines (P1 and P3) and protects against type 1 and type 3 wild polioviruses. Type 2 component from oral polio vaccine was removed as a part of global polio end game strategy.
On September 20, 2016, the Global Commission for the Certification of Poliomyelitis Eradication (GCC) also concluded that wild poliovirus type 2 (WPV2) has been eradicated worldwide, after reviewing formal documentation by the member states, global poliovirus laboratory networks and surveillance systems.
This led to the removal of the type 2 strain from all vaccines, converting the trivalent to a bivalent vaccine. The reason for the type 2 strain being removed from the trivalent vaccine is because more than 90 per cent of the vaccine-related outbreaks had been documented to have been caused by the type 2 strain and 38 per cent of vaccine associated paralytic polio (VAPP) have been due to this component.
As part of its polio immune strategy, government started giving fractional doses of injectable polio vaccine (IPV) which is 1/5th of the full IPV dose via the intradermal route in high performing states of the country since April 2016. These high performing states are Tamil Nadu, Kerala, Andhra Pradesh, Telangana, Karnataka, Orissa, Maharashtra and Puducherry.
As per the programme, two fractional doses of IPV are administered at 6 weeks and 14 weeks as an alternative to the intramascular injection of one full dose of IPV. Meanwhile, as part of the polio immune strategy, larger states are availing single dose of IPV through intramascular administration at 14 weeks.