The case of acute flaccid paralysis, likely due to polio, in a child from Tikrikilla in Meghalaya, and in the media spotlight, was reported by the State government on August 14. In April 2022, a case of vaccine-derived poliovirus was detected from an environmental sample collected in Kolkata. After genetic sequencing, it was considered likely to be immunodeficiency-related vaccine-derived poliovirus (iVDPV), excreted by an immune-deficient individual. In the Meghalaya incident, even after the government confirmed the case, there is still no official report on whether it is vaccine-derived and not caused by wild poliovirus. With the global eradication of the wild poliovirus (WPV) type 2 in 2015 and the WPV type 3 in 2019, respectively, and no WPV type 1 found in environment samples in India for years, it is highly unlikely that it is due to the WPV type 1 unless it has been imported into India. As of August 13, Afghanistan and Pakistan have reported 14 WPV type 1 cases this year. If vaccine-derived, there is again no official confirmation on whether it is iVDPV or from circulating vaccine-derived poliovirus (cVDPV). This information is key as cVDPV would mean that the virus is in circulation in the community, while iVDPV is restricted to the single immunodeficient child. Also puzzling is the absence of any official report on whether the case has been caused by the type-1, type-2 or type-3 vaccine-derived virus. India made the globally synchronised switch in 2016 from trivalent to bivalent oral polio vaccine that has only live, attenuated type 1 and type 3 virus. So, while it is impossible that the child has the type 2 virus from the oral vaccine given in India, the chances of cVDPV type 2 virus imported into India cannot be ruled out. In 2024, 68 cVDPV2 and four cVDPV1 cases were recorded globally. Many countries have reported cVDPV in environment samples.
The long delay in confirming these crucial details is intriguing as samples from the child were sent to the ICMR-NIV Mumbai unit, which is a part of the WHO network of 146 accredited polio laboratories worldwide and conducts research on diseases caused by enteroviruses, especially paralytic poliomyelitis and acute flaccid paralysis. Unlike in the case of IPV, immunodeficient children are not supposed to be administered OPV. Since identifying such children prior to administering OPV is a challenge in India, India will continue to have such cases in the future. The Meghalaya case again brings into focus the urgent need for India to stop using OPV and switch over exclusively to IPV. Most developed countries switched to IPV decades ago. There is no reason why India should not switch to IPV at the earliest.
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