Polio’s last stand

A health worker administers polio vaccination to children, in Karachi, Pakistan, 13 September 2019. (Keystone / EPA / Shahzaib Akber)

Decades of vaccination campaigns and billions of dollars have ended wild polio in Africa, health organizations announced last week. In 1996, when a push for eradication revved up in Africa, the disease was leaving an estimated 75,000 children paralyzed. Now, only Afghanistan and Pakistan still report outbreaks of wild polio. But, there’s a catch — one that researchers and the Geneva-based Global Polio Eradication Initiative hope to sort out.

Outsmarting a ‘very smart’ disease. Mutant strains of the disease have, on rare occasions, developed from the polio drops administered to children. Given unsanitary conditions and patchy vaccination coverage — often made patchier by the pandemic —  the weakened organism in the drops can become dangerous. Over the course of about a year, it can mutate and infect, paralyze or kill, just like the wild virus.

“Vaccine-derived” polio outbreaks have led to a few hundred cases in about 20 countries this year. Yemen and Sudan both reported new outbreaks of vaccine-derived polio in August.

“It’s a very smart organism… it will exploit any chink in our armour”, said Hamid Jafari, regional director for polio for the World Health Organization’s Eastern Mediterranean region.

“It exploits our weaknesses,” said Jafari, speaking to TNH from the United States.

Injectable polio vaccine doesn’t carry the risk of starting new outbreaks, as the virus doesn’t pass through the gut. But it’s not the easy solution it might appear to be: It requires refrigeration, plus a healthcare infrastructure and training to administer. In low-resource settings, all those things can be difficult to come by. If “a routine vaccination programme is not able to reach an infant; to open his mouth; to swallow a dose of OPV [oral polio vaccine], the same infant will not be able to… get an IPV [injectable polio vaccine] shot,” explained Emmanuel Vidor, vice-president for global public affairs for polio at pharmaceutical company Sanofi Pasteur — which manufactures IPV.

Vidor acknowledged the milestone of eradicating wild polio in Africa, but he said it would be a “little bit misleading” to say the hard work is over. Without being able to “extinguish” vaccine-derived polio outbreaks, the world confronts a potentially endless problem, he warned.

Searching for a final blow. To mop up these outbreaks and seal off polio’s chances of survival, new versions of the polio vaccine are under development. One of them, novel Oral Polio Vaccine type 2 (nOPV2), largely funded by the Bill and Melinda Gates Foundation (which also provides funding to The New Humanitarian), is almost ready for large-scale field use. It has passed preliminary trials. The WHO is considering granting the vaccine an “emergency use listing” – an expedited permission for large-scale field use.

That might happen before the end of the year. As Oliver Rosenbauer, communications officer for the Geneva-based Global Polio Eradication Initiative, told TNH on a call, work on the new vaccine started years ago. However, member states recognized the urgency of the situation, and in January called for faster development. “We had hoped to have it available much earlier, but then Covid had everything slowed down,” Rosenbauer said.

One possible country for nOPV2 early large-scale use is Sudan, Jafari told TNH, adding that they were about to commence formal talks with candidate countries.

Pandemic and polio. The COVID-19 pandemic and related lockdowns put polio immunizations on pause for about four months, Jafari said, adding that monitoring of suspected cases had for a while dropped by half.

It will take time to see if COVID-19-related disruptions in vaccination efforts hastened the spread of the disease. “It takes approximately one year of ‘silent circulation’… in order to have enough mutations” to become virulent, Vidor explained.

Mass vaccinations resumed in July in some key countries, Jafari noted, using new low-touch techniques to limit the risk of spreading one disease while eradicating another. The pandemic has made those campaigns more complicated and more expensive than previously, due to the need for more protective equipment and the slower tempo of vaccinations, he said. Helpfully, the extensive infrastructure of polio eradication efforts has been useful in battling COVID-19: For instance, polio teams in Pakistan, Jafari said, have been redeployed to work on public awareness, data management, and disease surveillance during the pandemic.