Two years without polio

In the 1980s, only three decades ago, 200,000 to 400,000 children, all under 5 years, were afflicted with polio paralysis annually in India. That was a daily average of 500 to 1000 cases. By the age of six, eight among 1,000 children already had polio paralysis; two would have died. In other words, one per cent of infants born were destined to develop polio.

Global movement

In 1988, India joined the global movement for polio eradication — at a time when we had not even succeeded in bringing polio under control. Control status required at least 95 per cent reduction. In 1978, India launched the Expanded Programme on Immunisation (EPI) with BCG and DPT vaccines. The oral polio vaccine (OPV) was introduced the next year. Natural polioviruses are called ‘wild’ to distinguish them from vaccine polioviruses that constitute OPV. Vaccine viruses are ‘attenuated’ from wild viruses — which means they have lost most of their ‘virulence,’ the ability to cause paralysis and the ability to spread fast among children. These two are the dreaded qualities of wild polioviruses.

By 1988, diphtheria, whooping cough and neonatal tetanus had declined to control levels as a result of EPI’s efforts. But polio did not come under control — showing that OPV was not as effective in India as in the West or in China. There, just three or four doses protected all children. In India, we had to give many more doses for equal effect. From 1994, India began nationwide OPV campaigns (called pulse immunisation) — two per year — to give additional doses to all under-five children irrespective of the number of doses already given. That resulted in effectively controlling polio by 2000. One of the three types of polioviruses, wild type 2, was even eradicated by October 1999 when the average number of OPV doses had reached six per child. The type 2 component of OPV was not only more effective against that type, but it also inhibited the effect of types 1 and 3.

That left India with the struggle to eradicate wild types 1 and 3 using a blunt weapon, the trivalent OPV (tOPV), containing types 1, 2 and 3, which is necessary to attack all three viruses simultaneously. In the Gangetic plain States, particularly Uttar Pradesh and Bihar, 9-10 pulse immunisation campaigns were conducted annually from 2004 to 2010. We then developed OPV containing just type 1 to make the tool sharper against the type 1 wild virus. That is called ‘monovalent OPV’ (mOPV-1). Eventually, India made ‘bivalent OPV’ (bOPV) with types 1 and 3. Remember, we did not have wild type 2 virus since 1999. With new tools and covering almost100 per cent children in their homes, while travelling, in brick-kiln and sugarcane fields where temporary migrant labour set up homes, wild polioviruses had no place to hide. We succeeded in stopping the transmission of type 3 in 2010 and type 1 in 2011. The last child with wild virus polio was detected in Howrah, West Bengal, with the onset of paralysis on January 13, 2011. Since then, only bOPV has been used for immunisation campaigns in U.P. and Bihar, while tOPV is used in routine EPI and national pulse immunisation campaigns twice each year.

How sure are we that wild polioviruses have been totally banished? There is a solid body of evidence to show this. All hospitals and clinics that attend to sick children have been networked to report any illness that even remotely resembles polio. Such illness is called ‘acute flaccid paralysis’ (AFP). Stool samples from every child with AFP are collected and tested for the presence of polioviruses. Every poliovirus so detected is further tested to distinguish wild poliovirus from vaccine poliovirus. When a lot of OPV is given to children, many with AFP would have vaccine polioviruses. That is to be expected. Sewage samples are collected every week from several wards of Mumbai, Delhi, Kolkata and Patna. During 2011 and 2012, all sewage samples were consistently negative for wild polioviruses (but with plenty of vaccine viruses). In northern India, the last footholds of wild polioviruses, the second half of each year was the season of high wild virus transmission. We passed two ‘high seasons’ in 2011 and 2012 without a single case. India has truly succeeded, silencing the many prophets of failure.

Highly contagious

Wild polioviruses are highly contagious — illustrated by some 50 episodes of international importations to countries that had once eliminated them using OPV. We had exported wild viruses to Nepal and Bangladesh in our neighbourhood, and to Bulgaria, Angola, China and Tajikistan, to name some distant ones. Now India is polio-free and vulnerable to importation from Pakistan, Afghanistan and Nigeria — the three countries that have not yet eliminated wild polioviruses. We cannot lower our guard and must continue pulse immunisations as though importation is imminent. India has five points of border-crossing with Pakistan: two in Jammu-Kashmir, two in Punjab, and one in Rajasthan. At every point, individuals are given one dose of tOPV when they enter India.

What was very remarkable was that India’s money went into the lion’s share of expenditure for polio eradication in the country, thus easing up global funds for use in other countries that needed them more than we do. India spent about Rs 1000 crore every year since 2000.

The rationale

Many have questioned the wisdom of spending such large amounts on one childhood disease. Was polio worth eradicating? From a humanitarian viewpoint as well as human rights angle no child deserved to be paralysed by a preventable disease. We know the struggle we had to go through merely to keep polio under control. Eradication is the best form of control. Once affected with polio, many children are neglected, do not complete high school, take up simple jobs like bicycle repair, managing telephone booths, etc.

The disability-determined productivity loss may be taken as about half of the gross domestic product per capita. That amounts to approximately Rs 50,000 per year; cumulated over 30 years of productive life, India was losing Rs. 15 lakhs per person — for a staggering Rs 45,000 crore per annum loss to the domestic economy from just one disease, polio, that affected 300,000 children each year. Controlling diseases that affect productivity is indeed a development activity. Eradicating polio is an investment. The absence of polio is both a measure of, and a means to, development.

The National Polio Eradication Certification Committee will confirm eradication of wild viruses and review the secure containment of laboratory storage of wild poliovirus strains or specimens likely to contain them before certifying India free of wild viruses. The Committee will wait for three years from the last virus detection before certification procedures, expected after January 2014. Thereafter, India will use only bOPV; later that will also be withdrawn, globally, synchronously. These rules of polio eradication ‘end game’ have been drawn up by the World Health Organisation and were endorsed by the World Health Assembly in 2012. In order not to create any polio immunity vacuum, the inactivated poliovirus vaccine will be introduced and sustained for at least five years. Polio eradication will then mean ‘no infection with any poliovirus, wild or vaccine.’

(The author was on the teaching faculty of Christian Medical College, Vellore, until retirement)

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Printable version | Sep 22, 2021 11:41:30 PM | https://www.thehindu.com/opinion/lead/two-years-without-polio/article4304903.ece

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