Achieving polio eradication in India: What’s next?


India was officially declared polio-free by the World Health Organization (WHO) on 25 February, 2012, as there were no reported cases of wild poliovirus in the past year [1]. Credit for this success goes to the oral polio vaccine (OPV) and the health personnel involved in this mass vaccination program over a prolonged time frame. OPV helped us become polio-free, but it will not keep us polio-free. This is because there is a risk of developing vaccine-derived poliovirus (VDPV) infections and vaccine-associated paralytic poliomyelitis (VAPP) from OPV. Now, the next challenge for India is to eradicate polio once and for all, and in order to do this, we need to deal with the VDPV and VAPP as well.

Key Point: India was excluded from the list of polio endemic countries by the WHO in 2012. Now is the right time for India to shift vaccines from OPV to IPV to reduce the cases of VDPV and VAPP to zero. Because IPV is made from inactivated polio virus, unlike OPV, there is no risk of vaccine-linked polio. Only by giving IPV can we ensure that India becomes truly free of all polio.

Incidences of wild polio infection in India

As of 13 January 2013, India had completed two years without any polio cases. This is a great improvement since India previously had nearly half of the world’s polio cases as recently as 2009! The polio cases decreased tremendously from 2003 to 2012, according to the recently published WHO EPI fact sheet. According to the report, the cases of wild polio decreased from 874 in 2007 to 0 in 2012. The last case of wild polio was reported in West Bengal on 13 January 2011 [2].

Risk associated with oral polio vaccine-derived poliovirus (VDPV) infections

As stated by the Global Polio Eradication Initiative, “Vaccine-derived polioviruses (VDPV) are rare strains of poliovirus that have genetically mutated from the strain contained in the oral polio vaccine.” [3] In 2011, 7 cases of VDPV were reported in India. [9] VDPVs are mainly of three types: circulating vaccine-derived poliovirus (cVDPV), immunodeficiency-related vaccine-derived poliovirus (iVDPV), and ambiguous vaccine-derived poliovirus (aVDPV) [3]. A total of 20 cVDPV outbreaks occurred, resulting in 580 polio cases occurred between 2000 and 2011. The iVDPV is defined by a prolonged replication of vaccine-derived viruses over a period of time by children with rare immunodeficiency disorders. Only 33 cases of iVDPV have been reported so far worldwide. Very little information is available regarding the aVDVP, whether it is excreted by immunodeficient people or isolated from the sewage of unknown origin [3, 4]. Vaccine-associated paralytic poliomyelitis (VAPP) is estimated to appear in about 1 in 2.7 million children who receive their first dose of OPV [3].

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