Kerala, along with seven other States, has launched the second phase of the inactivated polio vaccine (IPV) programme under routine immunisation (RI), as part of the Global Polio Endgame Strategic Plan of the WHO.
Accordingly, beginning April 1, infants aged 14 weeks and above are being given a dose of IPV under the routine immunisation schedule, along with three doses of oral polio vaccine (OPV) in the primary vaccination series, in the States of Kerala, Odisha, Andhra Pradesh, Telangana, Karnataka, Tamil Nadu, Puducherry and Maharashtra .
IPV was introduced in the country under RI on November 30 2015, and six States were chosen for its launch in the first phase. The Global Polio Endgame Strategic Plan deals with the eradication and containment of polio caused by wild polio viruses as well as that caused by vaccine-derived polio viruses linked to the oral polio vaccine.
Accordingly, all nations have to introduce one round of IPV into the RI schedule, followed by a globally synchronised replacement of trivalent OPV (effective against polio types 1,2,3) with bivalent OPV (effective against type 1,3).
Last such case in Kerala in 2000
The last case of polio due to wild virus was reported in Kerala in 2000. India has been polio-free for the past five years, thanks to the consistent pulse polio immunisation programme using trivalent OPV. The OPV uses a live but weak strain of polio virus for immunity. A risk associated with using OPV is that live viruses can undergo genetic changes in the intestine and become virulent. In communities with low routine immunisation, such mutated viruses or vaccine-derived polio viruses (VDPVs) can cause paralytic polio in unimmunised children. In 2011, seven such polio cases caused by mutated OPV viruses had been reported in India.
Wild polio virus type 2 was declared eradicated worldwide in 1999, and hence, continued use of the live type 2 vaccine component in the trivalent OPV poses the risk of polio caused by mutated type 2 viruses. This is the reason why trivalent OPV is being replaced by bivalent OPV which contains only type 1 and 3 viruses
“The global switch from trivalent OPV to bivalent OPV is scheduled to take place between April 17 and May 1. In India, this nationwide switch is scheduled for April 25, after which trivalent OPV will cease to be used,” a senior Health official said.
