Is India actually free of polio?

Why New Delhi must not bask in the WHO’s polio-free certification and, instead, have an ambitious plan to eradicate polio-like flaccid paralysis.

December 04, 2015 01:58 am | Updated March 16, 2020 02:21 pm IST

On November 30, the day India introduced an Injectable Polio Vaccine (IPV) in its routine immunisation programme, stating that it “will be an important step in the Polio Endgame Strategy”, a case of Vaccine Derived Polio Virus (VDPV) was reported from New Delhi. This was the second such case to be reported this year.

India has not reported a single case of polio caused by the wild polio virus (WPV) since January 2012. It is important to note that it also received a polio-free certificate from the World Health Organisation (WHO) in 2014, after a nervous two-year wait to establish that the country can indeed maintain its polio-free status.

The polio virus causes paralysis — medically known as an acute flaccid paralysis (AFP) — which is characterised by sudden muscle weakness, and fever in one or more limbs. AFP can occur due to many reasons, one of which is vaccine-linked.

Vidya Krishnan

Hollow status Between January 2014 and March 2015, India reported four cases from four different States, of vaccine-derived polio. This is not all. Until November this year, the country has reported 36,968 cases of non-polio AFP. For those who follow the sector, this is neither news nor surprising. There has been a surge of non-polio AFP since India eradicated polio. The number of cases reported in 2012 was 59,436, in 2013 it was 53,421, and in 2014 it was 53,383.

Three years after India reported its last case of WPV, the country has, in one form or another, been reporting around 50,000 cases of flaccid paralysis that, clinically, is exactly like polio, indicating how hollow the polio-free status is.

According to an article in the American journal Pediatrics , there is an undeniable link between the increase in incidence of NPAFP (non-polio AFP) and the number of OPV doses delivered in any region. Oral polio vaccine (OPV) contains an attenuated (weakened) vaccine-virus. The weak form of the polio virus is used to activate an immune response in the body, which then protects the child when challenged by WPV. But when a child is immunised with OPV, the weakened vaccine-virus replicates in the intestine. During this time, the vaccine-virus is also excreted. In areas of inadequate sanitation, this excreted vaccine-virus can quickly spread in the community and infect children with low immunity. This excreted vaccine undergoes genetic changes as it circulates in the community and causes VDPV.

The cases of VDPV are rare as it has to circulate for a long time in the community of under-immunised populations before it can infect and cause paralysis in someone.

Low vaccination coverage To be clear, the problem is not with the vaccine itself, but low vaccination coverage. That VDPV is circulating in the community that is under-immunised marks the failure of the Central government — which even in best case scenarios has achieved only 70 per cent immunisation coverage, leaving a massive cohort susceptible to poliovirus, vaccine derived or otherwise.

At present, the government’s only strategy to combat the invisible kinds of polio is the addition of IPV. As per the WHO norms, the best way to cope with cases of NPAFP and VDPV is a synchronised switch from trivalent to bivalent Oral polio vaccine, which India has already done. To further prevent the risk of re-emergence, a booster dose of inactivated polio vaccine (IPV) is recommended in routine immunisation, prior to the switch.

A 2005 study in the Indian Journal of Medical Research on NPAFP found that a fifth of cases of NPAFP were reported from Uttar Pradesh. On follow-up after 60 days, researchers realised that 35.2 per cent children had residual paralysis and 8.5 per cent had died (making the total of residual paralysis or death a startling 43.7 per cent. This means that children who had NPAFP are more than twice at risk of dying than those who get infected with WPR.

We may be polio-free but we are reporting the world’s largest number of NPAFP. Realistically speaking, we need an urgent policy intervention to address NPAFP and VDPV with the same urgency and political will with which we addressed the wild polio virus cases.

For now, unfortunately, the government is still basking in the glory of one of its rare public health achievements since Independence, and is patting itself on the back for eradicating polio even while cases of flaccid paralysis have seen a serious resurgence. For a parent whose child has been diagnosed with flaccid paralysis polio or the non-polio kind, nomenclature offers little consolation.

Which begs this question, what is the value of this polio-free certification when nearly 50,000 children fall prey to polio-like flaccid paralysis every year?

vidya.krishnan@thehindu.co.in

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