Eradicating Polio

The WHO Collaborating Centre for Global Health Histories, supported by the Wellcome Trust, has produced a series of seminars in association with the WHO HQ, WHO Regional Offices, WHO Country Offices and national governments.  

One seminar, shown at a major WHO EURO event, focuses on the move towards world eradication of poliomyelitis and why this has still not been achieved, 20 years after the originally stated goal of 2000.

 

The seminar can be viewed and/or listened to here:

Global Health Histories Seminar 110: Polio, immunization and universal health coverage, University of York

Speaker(s): Thomas Abraham (Director, Public Health Communication Programme, Journalism and Media Studies Centre, the University of Hong Kong) and David Heymann (London School of Hygiene and Tropical Medicine, and Head of the Centre on Global Health Security at Chatham House & formerly WHO Assistant Director-General)

 

 

This briefing draws on the presentations at that seminar.

 

On 25 August 2020, the Africa Regional Certification Commission certified the WHO African Region as wild polio-free, after four years with no cases of wild poliomyelitis (polio) in the region. Over 90 per cent of the world’s population is now free of wild poliovirus, and only 33 cases were reported in 2018. However, Africa still faces the challenge of vaccine-derived polio, which as of October 2020 was present in 14 countries of the region.

 

Many people consider that polio eradication would constitute a major advance. There are three strains of wild poliovirus, each of which requires a specific vaccine to be eradicated and all of which cause paralysis. The disease mainly affects children, with roughly one in 200 wild poliovirus infections leading to irreversible paralysis. This is most often in the legs, but the brain and/or the breathing muscles can also be affected. At the same time, the majority of infected children are asymptomatic. “Whereas smallpox, for instance, is very easy to identify because it leaves pockmarks all over the body, for every child who is paralysed by polio there are 600 to 1,000 children who are infected and can transmit the disease to others but who show no signs whatsoever,” explains David Heymann (Professor of Infectious Disease Epidemiology at the London School of Hygiene and Tropical Medicine, head of the Centre on Global Health Security at Chatham House and formerly WHO Assistant Director-General, with responsibility for polio eradication).  

 

In 1988, the World Health Assembly (WHA) passed a resolution to eradicate polio globally by 2000, describing this as ‘an appropriate gift … from the twentieth to the twenty-first century’. Type 2 was eradicated in 1999 and no case of type 3 has been found since the last reported case in Nigeria in November 2012. However, more than 20 years after the start of this century there is still endemic transmission of type 1 wild poliovirus in border areas of Afghanistan and Pakistan, and the WHO estimates that failing to eradicate polio from these areas could mean that polio spreads again, causing up to 200,000 new cases a year worldwide within 10 years.

 

“The polio programme itself is, as ever, optimistic. The message is that the incidence of polio has been reduced by 99 per cent from the time the programme was launched, and that is absolutely true,” says Thomas Abraham (Director, Public Health Communication Programme, Journalism and Media Studies Centre, the University of Hong Kong and author of Polio: The Odyssey of Eradication. “But in two countries it has not been interrupted, and at the same time vaccine-derived polio cases are repeatedly popping up in areas that were once thought to be polio-free.”

 

 

A sudden WHO priority

Abraham is particularly interested in how the decision by the WHA to eradicate the disease came about in. “On one level it's as clear as daylight: 1988 the World Health Assembly voted to try and eradicate polio by the year 2000, at another level it is really mysterious.”

 

The proposal to eradicate was made by WHO Director-General Dr Halfdan Mahler, only three weeks before his departure from the post, in a speech to the World Health Assembly in1988. The occasion was the 40th anniversary year of the WHO and the 10th anniversary of the declaration from the Alma-Ata International Conference on Primary Health Care, which had expressed ‘the need for urgent national and international action to protect and promote the health of all’.

 

However, Abraham points out, this was a quite surprising focus for Mahler, who had said publicly and repeatedly that the smallpox eradication programme was the last single-disease eradication programme to which the WHO would commit its resources. “His philosophy was completely different; that same money, he felt, was much better spent by building up health systems, especially at the village level. He firmly believed that the decision on which diseases ought to be tackled first was something that really should be determined at the levels of communities and not by big organisations sitting in Geneva or New York. For him, eradication programmes represented everything that was wrong with healthcare.” 

 

Yet suddenly, Mahler made a quite unexpected public commitment to eradicating polio within the next 12 years. “It was not even on the agenda initially. One of the most consequential decisions that the World Health Organization has taken was actually done pretty hastily – and it was also a really low-key resolution, saying that countries were ‘invited to formulate and consider plans for vaccination coverage in order to make this happen’. “There’s no paper trail to explain how this change happened, and the decision was hastily taken” This was in sharp contrast to the activity that preceded (and indeed succeeded) the resolution to eradicate smallpox.” 

 

Heymann offers another reason for Mahler’s change of mind. The Global Polio Eradication Initiative is a public-private partnership led by national governments with six-core partners – the WHO, Rotary International, the US Centers for Disease Control and Prevention, UNICEF, the Bill & Melinda Gates Foundation and Gavi, the Vaccine Alliance. Rotary International has been a particular driver in this. “Some of the Rotary groups from the US went to the Philippines back in the mid-1980s on an exchange programme, where they saw children paralysed from polio which had been gone from the US for almost 20 years. They became great advocates for getting rid of polio – they actually went over and helped in the vaccination programmes – and it was Rotary International which really pulled together a partnership with UNICEF, the WHO and the Center for Disease Control to tackle it. I would think it was Rotary that convinced Mahler that this was an important thing to do.” 

 

Immunisation and wider strategies

The polio eradication programme was linked to the WHO’s wider immunisation programme, which aimed to ensure that by 1990 every child would be immunised against diphtheria, pertussis (whooping cough) and tetanus. “The resolution said it should be pursued in ways to strengthen this integrated immunisation programme,” Heymann explains. “Polio was meant to be the sail if you like, and the wind hitting these sails would push the entire boat to shore,” Abraham adds. It was also an easy vaccine to deliver (unlike, for instance, smallpox vaccine) because it was given in oral drops and did not require trained health care workers to immunise children.

 

However, at the start of the programme access to polio vaccine varied hugely. In some richer countries it was offered routinely to children; conversely, in a number of WHO regions (Africa, the eastern Mediterranean and Southeast Asia) polio immunisation rates were far too low to produce herd immunity (which requires around 90 to 95 per cent immunisation). In addition to routine immunisation, the programme supported national immunisation campaigns to increase coverage. 

 

The other strategy in the eradication programme was a highly sophisticated surveillance programme using cutting-edge technology. A network of national and regional laboratories around the world took poliovirus isolated from stool specimens – including specimens taken from the Mumbai sewers – analysed them using genetic sequencing and stored the results in a shared global database. “That sequencing is very important because the poliovirus mutates at a steady rate as it transmits through humans and each type has many sub-families as a result,” says Heymann. “Genetic analysis means it’s easy not only to see what those mutations are but to trace back to see where the virus might have originated. For instance, in Pakistan they were actually able to find cases of polio in 2010 that could be linked back to cases in 2009 genetically; and that meant it was possible to go back to the place where this virus was thought to originate and make sure that it had indeed been eliminated from that area.”

 

Vaccine-derived polio

There is a further issue in that the oral form of polio vaccine contains a weakened form of the live poliovirus, which is excreted from the body. In places which do not have adequate sanitation this virus can spread to other people, and in areas where there is not a high enough immunity in the local population, the virus circulates and can mutate into a new active strain: a circulating vaccine-derived virus (cVDPV). 

 

As a result, in addition to the wild poliovirus still in circulation, cVDPV has become a major stumbling-block in the journey towards eradicating the disease. “In fact, now cases of vaccine-derived polio are greater than the number of wild polioviruses,” Abraham points out. “I think this is really worrying.”

Vaccination opposition

However, many vaccines have met with considerable opposition and polio is no exception. In 2003 wild polio had been absent from the state of Kano in northern Nigeria for four years when the state governor announced that he had read online that the vaccine made young girls sterile. “He saw this as a plot being run through the UN agencies which were controlled by Western countries,” says Heymann. “As a result, polio spread from Nigeria all the way across into Indonesia, through trade and religious pilgrimage groups. So, countries that had been polio-free became infected again. It was very hard to get polio activities restarted in northern Nigeria.”

 

Two laboratories, based in South Africa and India, which worked with the WHO – but crucially were not part of the WHO, as the WHO was considered part of the problem – offered to test the vaccine for the government of Nigeria. Their results showed no impurities which might cause sterility, but the Nigerian national vaccine expert group refused to accept this. A resolution from the Organisation of the Islamic Conference (now the Organisation of Islamic Cooperation), high-profile vaccinations and requirements from Saudi Arabia that all pilgrims entering the country were vaccinated all failed to change the governor’s views. Finally, a resolution from the WHO in 2008 and the subsequent pressure from within Nigeria did push him to rescind his views, but vaccine refusal continued for some time. 

Priorities, context and the future

Abraham also highlights another problem; that for many people, polio simply isn’t as important a priority as other conditions. He cites a man he met in northern Nigeria, who agreed to have his children vaccinated against polio. “Then he burst out later saying: ‘Polio, polio, polio. Why polio? When my child has a fever, the nearest public health centre is 10 kilometres down the road; I need to go to the main road and find a lift or a bus or get someone to take me there. When I get there, there are no medicines. But people are coming here every day and pressing polio drops on me.’ Children are dying of other things – malaria, measles, diarrheal diseases. These are the real killers, for many people, but they just see all the emphasis on polio, and it doesn’t make sense to them.”

 

Despite this, however, wild polio is nearly eradicated. Heymann flags up final concerns. “Strong leadership and innovation have been instrumental in stopping wild poliovirus. Countries have successfully coordinated their efforts to overcome major challenges such as high levels of population movement, conflict and insecurity restricting access to health services, and the virus’s ability to spread quickly and travel across borders. But the polio endgame has been slowed by vaccine-derived polio; we now have a world where vaccine-derived polio is equally as important as wild poliovirus.” 

 

What’s more, there is a considerable amount of the virus – both wild and polio-derived – either taken from the vaccine or from stool samples, which is still stored in laboratories around the world. “And there is one last sobering issue about polio eradication,” Heymann concludes. “Even after wild poliovirus is gone and vaccine-derived poliovirus is gone and all the poliovirus in these laboratories has been locked up or destroyed there will still be a risk because the poliovirus has actually been synthesised in a laboratory way back in 1991, just using the genetic sequence. It will still be possible to construct a new poliovirus. So, polio has had many challenges: and the final challenge is both when will eradication finally be completed and whether the disease will remain permanently eradicated.” 

 

Radhika Holmström is a Wellcome Trust-funded writer and communications specialist working with the WHO Global Health Histories project at the University of York.