On the day the Centre launched an injectable vaccine as the final onslaught against eradication of the polio virus, Delhi government authorities confirmed the diagnosis of a rare Vaccine Derived Polio Virus (VDPV) in a two-and-a-half year old child.
The child, who lives in Shahadra’s Harsh Vihar area, was diagnosed with the P2 strain of the virus around three weeks ago. The last recorded case of VDPV was reported from Beed, Maharashtra, in 2013.
According to sources, the child received 20 doses of the oral vaccine as part of his routine immunisation. In his case, the live attenuated virus from the vaccine started to actively circulate in the body. The P2 strain, considered the strongest of the three strains of the polio virus, was the first to be eliminated from India in 1999.
Dr C M Khanijo, officer on special duty, pulse polio cell of the Delhi government, said, “The child’s diagnosis was confirmed on November 3, and within two days, we started surveillance and initiated a supplementary polio immunisation round in adjoining areas.”
Doctors said the child was found to have poor immunity. “We tested all his parameters. The child was immunodeficient. It is usually such children with poor immunity who, in rare cases like these, contract the virus from the vaccine,” Dr Khanijo said.
The oral vaccine, which has three live attenuated strains of the polio virus, has a one-in-over-2.5 million chance of causing VDPV. Only about 45 such cases have been reported in the country till date. The injectable vaccine launched on Monday comprises three heat killed strains of the polio virus, which cannot lead to active circulation of the virus in the body.
Authorities have carried out tests in the vicinity to rule out environmental spread of the virus. Sources said 36 stool samples have been collected from the family and other children who were in contact with the child. Samples have also been taken from seven sewage sites to check for the virus. “We have collected as many samples as possible from young children and family members who have been in close contact with the child. All samples have been negative, which establishes that the virus is not circulating in the environment,” Khanijo said.
Dr Rajesh Kumar, chief district medical officer of Shahadra district, confirmed that a special polio immunisation drive from November 6-10 was held in Northeast and East Delhi after the case surfaced. “Polio officers directed us to help in a special polio immunisation drive in the area after this case surfaced. We are still monitoring children in the area,” Kumar said, adding that the affected child would be provided necessary treatment and support.
Union Health Ministry officials held a meeting with Delhi government authorities on November 4 after the diagnosis was confirmed, sources said. The injectable vaccine has been launched in an effort at total eradication to ensure that there are no vaccine derived cases. “The priority of the programme is towards environmentally derived or wild polio virus cases. This is a very rare vaccine derived case where we have taken all necessary contingency measures,” Dr Khanijo said.
What is vaccine-derived polio
Oral polio vaccine contains an attenuated (weakened) but live vaccine-virus, activating an immune response in the body. In rare cases, when the child’s immunity is low, the virus can start circulating actively in the body of an immunised child. In areas of inadequate sanitation, excreted vaccine-virus can spread in the immediate community before eventually dying out. On rare occasions, if a population is seriously under-immunised, an excreted vaccine-virus can continue to circulate for an extended time. Source: WHO