Sapthagiri Institute of Medical Sciences and Research Centre (SIMS & RC) in collaboration with the National Polio Surveillance Project of WHO-India (NPSP-WHO), Bengaluru unit and Government of Karnataka have now highlighted the safety of the new injectable polio vaccine.
 
The daylong event deliberated on various issues concerning immunization like the recent switch from tOPV to bOPV, introduction of IPV into routine immunization, plans for future regarding polio eradication, eradication of other diseases etc. These issues were addressed by Dr Asish KSatapathy, regional team leader, south region, B P Subramanya, SMO, Dr Lokesh, SMO, all from WHO-NPSP, Dr Sudarshana, BBMP immunization officer, Dr Mahesh Kumar, district RCH officer. There was also a talk on research opportunities in cold chain by Dr Balu, professor from JJMMC, Davangere.
 
At a Continuing Medical Education Programme titled “Immunization Transition: Present and Future” organized by the Department of Community Medicine, SIMS & RC, benefited 180 doctors- academicians, researchers, general practitioners from across Bengaluru.
 
A panel of experts pointed out that considerable progress had been made in reducing polio transmission, particularly India being certified as polio-free from March 2014. The eradication of type 2 polio virus was declared in September 2015. Trivalent Oral polio vaccine was replaced by bivalent polio vaccine. The key reason for this was that polio is caused by type 2 virus component which has been eradicated in 1999.
 
About 80 per cent of vaccine-derived polioviruses (VDPVs) are rare strains of poliovirus that have genetically mutated from the strain contained in the oral polio vaccine. Since the cases due to wild polio virus have reduced to almost nil, what remains is to control this VDPV by giving injectable polio vaccine. Rest of the risk of VDPV will only be eliminated when use of OPV is ultimately stopped, that is the aim finally, said the panel.
 
The switch refers to the replacement of all tOPV containing attenuated poliovirus serotypes 1, 2, and 3 with bOPV that contains types 1 and 3 only in routine immunization and supplemental immunization activities (SIAs), in every country.
 
Both vaccines have been administered to billions of children and have excellent safety profiles. Both are administered orally. The objective of the switch is to stop the emergence of cVDPV2 which is known as circulating vaccine derived polio virus and VAPP referred to as the vaccine associated paralytic polio caused by the attenuated type 2 strain of tOPV.
 
The type 2 component of Oral Polio Vaccine (OPV) has been phased out from all immunization activities in a globally coordinated manner. The planned withdrawal of the type 2 component of tOPV is part of the global polio eradication endgame strategy for 2013-2018. Since November 2015, single dose of IPV is being administered along with 3rd dose of DPT and OPV at 14 week age. Studies in Cuba and India have proved that even single dose of IPV can result sero-conversion in 63% of infants who received this as only dose of polio vaccine. Those who have received OPV earlier, this sero-conversion may be to the tune of 98-99 per cent.
 
The introduction of IPV will help to reduce risks associated with the withdrawal of OPV type 2, facilitate interruption of transmission with the use of monovalent OPV type 2 in the case of outbreaks, and hasten eradication by boosting immunity to poliovirus types 1 and 3.Ultimate step in 'Polio end game strategy' is to stop the use of OPV and switch to IPV in toto. It involves enormous costs to nations but the cost of human suffering was much more with polio.