A nine-month-old in Mumbai has become the fourth case of vaccine-derived polio virus type 2 in the country this year. The child is on ventilator and all four of his limbs are paralysed. “We are now testing other children in his home and locality,” said Satish Pawar, the director, directorate of health services to the paper. “If he has a compromised immunity, the live virus in the vaccine can keep on multiplying and any mutation in the virus could lead to the disease.”
Vaccine-derived polio viruses are rare strains of polio virus that have genetically mutated from the strain contained in the oral polio vaccine. The central government is considering the introduction of an injectable vaccine called inactivated polio vaccine (IPV), which will contain a strain of the virus that has been killed, along with the oral polio vaccine (OPV).
Vaccine-derived polio viruses usually begin because of low immunity in the population. Because of lack of immunity, the vaccine-virus can continue to circulate in the body for an extended period of time. The longer it is allowed to survive, the more genetic changes it undergoes. In very rare instances, the vaccine-virus can genetically change into a form that can paralyse – this is what is known as a circulating vaccine-derived poliovirus (cVDPV).
According to the World Health organisation and the Global Polio Eradication Initiative, VDPVs can be prevented with the regular administration of oral polio vaccines to infants and children.
