The battle against polio will turn over a new leaf with the health ministry deciding to switch over to bivalent oral polio vaccine (OPV) from the presently administered trivalent OPV from April 25. The trivalent oral polio vaccine has been in the immunisation schedule since 1978 and was available for use in India from early 60s. With the switch over and simultaneous introduction of single dose of injectable polio, the country aims at complete eradication of poliomyelitis by 2020.
“A total of 156 countries, including India, will be switching to bivalent oral polio vaccine from April 25. The real challenge now is to collect entire stock of trivalent oral polio vaccine and dispose them scientifically,” Ravindra Banpel, World Health Organisation’s (WHO) regional team leader (western region) told Times of India..
Bivalent oral polio vaccine has been in use as a supplementary immunisation activity in country’s high-risk areas.”Now that we are going to completely switch over to bivalent, a slew of workshops are currently underway to train and sensitise the health staff about what the switch actually means and why it matters,” Banpel said.
Senior paediatrician Sharad Agarkhedkar said, “Union health ministry has advised all doctors working in public as well as private healthcare units to switch the use of trivalent (tOPV) to bivalent polio dose (bOPV). The all available t-OPV vaccines will be destroyed by boiling or autoclaving.”
The supply of tOPV will stop after April 1 in the private market and bOPV will be made available from April 10. However, bOPV is not to be opened or used before the `switch date’. There should be complete disposal of tOPV within two weeks of the switch (April 25). The Union government has issued nationwide guidelines for the proper disposal of tOPV.
“Oral polio vaccine (OPV) has been instrumental in successful control of paralytic polio. However, a rare but serious adverse effect associated with OPV is Vaccine Associated Paralytic Poliomyelitis (VAPP).Another major problem with he use of OPV is the emergence of Vaccine-Derived Polio Vi ruses (VDPVs),” said senior paediatrician Pramod Jog, national president of the Indian Academy of Paediatrics (IAP) and chairman of the IAP’s Advisory Committee on Vaccine and Immunisation Practices. In 1985, Jog had launched a campaign `Goodbye Polio’ starting from Pune.
VDPVs arise due to mutation and recombination in the human gut and are 1-15% divergent from the parent vaccine virus. These viruses are neurovirulent and are transmissible and capable of causing outbreaks. For this reason, it is of paramount importance to discontinue the use of OPV after polio eradication has been certified.
India is on the verge of complete eradication of poliomyelitis, the last reported case of wild polio virus disease was in January 2011.
“With the switching over to bOPV and simultaneous introduction of single dose of injectable polio vaccine, we are aiming at complete eradication of poliomyelitis. Thereafter, oral polio vaccine would be completely withdrawn and replaced by injectable polio vaccine, as being currently practised in the developed countries,” said paediatrician Jayant Joshi, president of Pune branch of the IAP .
“Among 686 cases of paralytic polio caused by circulating vaccine derived polio viruses (cVDPVs) that have been detected since 2006, type 2 cVDPVs (cVDPV2s) accounted for 97% of the cases,” said paediatrician Rajeev Joshi.
To eliminate the risks posed by cVDPV2s, OPV serotype 2 will be withdrawn from all immunization activities through a global, synchronized replacement of all tOPV with bivalent OPV . “Eventually , we want to get rid of the polio virus, be it wild virus or vaccine virus. So the bivalent oral polio vaccine will be replaced by injectable polio vaccine by 2020 which will eliminate all types of circulating polioviruses and the adverse events caused by the current oral polio vaccine,” said paediatrician Sanjay Lalwani, head of the paediatrics department at Bharati hospital.