The wild poliovirus is “cornered” in the last two countries where it is found, a leading expert has said as efforts continue to eradicate the pathogen.
In a briefing to mark a decade since India was declared polio-free, clinicians have said that progress is being made to eliminate the virus in the last two nations where it is endemic – Pakistan and Afghanistan.
With flare-ups remaining a threat even in high-income nations, clinicians say there is no room for complacency in the battle against the sometimes-fatal disease.
The UAE has been one of the leading players in the fight against polio, having financed vaccination efforts and supported initiatives to mobilise international action.
Polio vaccination drive in Pakistan – in pictures
Poliomyelitis primarily affects young children who, in severe cases, may become paralysed or even die after contracting the virus.
“We have Pakistan and Afghanistan [where polio is] still endemic, but the virus is cornered in very few pockets in very few districts,” Dr Ananda Bandyopadhyay, deputy director of polio technology, research and analytics at the Bill & Melinda Gates Foundation, said.
Dr Bandyopadhyay said there had been more than 10 genetic families of the virus in these two countries, but this has now fallen to two.
“It indicates the virus is cornered,” he added.
Continued efforts to vaccinate populations have been credited with helping to eliminate pockets of the disease in Afghanistan and Pakistan.
However, there can be hazards for people engaged in the vaccine roll-out in these two nations. Anti-vaccine sentiment has even resulted in the murder of medical staff engaged in immunisation efforts and of police protecting them. The wild poliovirus can also continue to circulate in some areas where populations are hard to reach.
An injectable inactivated polio vaccine was introduced in 1955, with the oral polio vaccine, taken as drops in the mouth, following six years later.
Investing in global polio fight
In 1988, more than three decades after vaccination efforts began, there were still, World Health Organisation figures indicate, 350,000 cases caused by wild poliovirus, which remained endemic in 125 nations.
That year saw the launch of the Global Polio Eradication Initiative led by the WHO, the UN children’s fund Unicef, Rotary International, the US Centres for Disease Control and Prevention (CDC) and the Bill & Melinda Gates Foundation.
Continued efforts resulted in India and the WHO’s South-East Asia region being declared polio-free in March 2014.
Some thought that, in a country as large as India, where many live in absolute poverty, it would be impossible to eliminate polio.
“People used to tell us it was a pipe dream,” Dr Hamid Jafari, director of polio eradication for the WHO’s Regional Office for the Eastern Mediterranean, said.
“The eradication of polio in India proves beyond doubt the biological and technical feasibility of polio eradication.”
He said that lessons learnt in India have been applied to the other remaining countries where the wild poliovirus circulates.
Another major milestone was reached in June 2020, when Nigeria, one of just three countries where wild poliovirus still circulated, was declared polio-free.
The oral polio vaccine contains a weakened form of the polio virus that in rare cases mutates, becomes pathogenic and circulates in poorly immunised populations, causing circulating vaccine-derived poliovirus (cVDPV). In a very small proportion of cases this, like the wild poliovirus, can cause paralysis.
In recent years there have been cases of cVDPV even in high-income nations including Israel, Britain and the US.
The UK and the US administer an inactivated polio vaccine and do not use the oral polio vaccine, so cases of cVDPV in these nations are thought to have emerged from the virus being brought in.
In March 2021 the novel oral polio vaccine type 2 (nOPV2) was introduced on an emergency basis, representing a step forward because it is genetically stable, reducing the risk of cVDPV. About a billion doses of nOPV2 have now been administered in 35 countries.
The UAE has been one of the leaders in the fight against polio, with the UAE Pakistan Vaccination Assistance Programme having delivered over half a billion vaccine doses in the South Asian country over the past decade.
Since 2014 President Sheikh Mohamed has contributed hundreds of millions of dollars to vaccination and polio eradication campaigns.
In 2013 Abu Dhabi hosted, in partnership with Ban Ki-moon, then the UN secretary-general, and Bill Gates, the co-chair of the Bill & Melinda Gates Foundation, a groundbreaking Global Vaccine Summit where $4 billion was pledged to support the fight against polio.
Dr Jay Wenger, director of polio at the Bill & Melinda Gates Foundation, said that efforts had to continue to try to eradicate the disease.
“We have to push to the end or we won’t quite make it,” he said.
