A boy receives polio vaccine drops at a railway station in Karachi, Pakistan. Photo by: REUTERS / Akhtar Soomro

MANILA — The Global Commission for the Certification of the Eradication of Poliomyelitis announced on Thursday that wild poliovirus type 3 has now been eradicated worldwide. But those who’ve been working on the disease’s eradication caution the job is far from over.

“It shows progress, but complacency is one of our biggest dangers now. And the last thing we want is to highlight the job is done. The job is not done. There is still wild poliovirus type 1 that needs to be eradicated,” Oliver Rosenbauer, WHO communications officer and spokesperson for the Global Polio Eradication Initiative, told Devex.

Wild poliovirus type 3 is one of three wild poliovirus strains, and is the second to be eradicated worldwide. Wild poliovirus type 2 was eradicated in 2015. This leaves only wild poliovirus type 1 still in circulation in Pakistan and Afghanistan.

Strains of wild poliovirus type 3 will be kept in a limited number of laboratories worldwide with the proper containment measures in place, said Rosenbauer. The declaration won’t impact routine immunizations, at least not immediately. This is unlike when type 2 wild poliovirus was eradicated in 2015 and governments agreed to phase out the vaccine containing its antigen in 2016, switching from the trivalent oral polio vaccine to the bivalent oral polio vaccine.

While there is risk of a circulating vaccine-derived poliovirus type 3, Rosenbauer said this is “extremely, extremely rare” compared to the risk associated with vaccine-derived poliovirus types 2 and 1. Over 90% of circulating vaccine-derived polio outbreaks are due to the type 2 component of the vaccine, while about 8% are due to the type one component, he said.

“But that risk does exist. So that is why, ultimately, we need to stop the use of [the oral polio vaccine] altogether eventually, to get rid of the risk of any type 2, type 3, or type 1 circulating vaccine-derived polio virus emerging,” he said.

Strains of vaccine-derived polio remain a concern, with 95 cases reported since January 2019 — more than the 88 cases of wild poliovirus found in Pakistan and Afghanistan. Like wild poliovirus, these strains can also paralyze children.

For Pro subscribers: DevExplains: Vaccine-derived polio and the challenge of eradication This year there have been 95 cases of circulating vaccine-derived polio cases in 12 countries in Asia and Africa, exceeding the 88 cases of wild poliovirus in Pakistan and Afghanistan. But the world continues to use the oral polio vaccine. Why and how can vaccine-derived polio cases be prevented?

“Anytime that you have a polio outbreak in a previously polio-free area, it's a setback, because you need to do an outbreak response. And that detracts resources away from where we would like to spend our resources, which is in the endemic countries of Pakistan and Afghanistan,” Rosenbauer said. Resources, he explained, means financial and technical resources, as well as vaccine availability.

The initiative’s spokesperson said the world is likely to witness more outbreaks “before we are fully done” with polio.

“Abandoning the effort now will not keep things at the current level. We will get a major resurgence. And that's what we need to explain to people: Don't think if you stop, it will be over. It will not be over and it will get a lot worse,” Walter Orenstein, associate director of the Emory Vaccine Center and director of Emory’s vaccine policy and development, told Devex in a separate interview.

But as long as there’s wild poliovirus circulating in the environment, the use of oral polio vaccine that contains a weakened form of the viruses will need to continue.

‘We need the international community to stay engaged’

The last time a strain of wild poliovirus type three was detected was in November 2012 in Nigeria. What the country did to eventually rid itself of the virus, however, could be useful for the remaining polio-endemic countries of Pakistan and Afghanistan, Rosenbauer said.

“I think one thing that the government of Pakistan is now doing, which I think is the right approach and it's something that Nigeria started doing several years ago as well, is kind of move … to a targeted approach, and to look at area by area why are children being missed.

“Is it because of population movements in this area? Is it because of insecurity? Is it because of community resistance? Is it because of lack of vaccines … because the cold chain isn't properly set up?” Rosenbauer said.

This work is vital, he said, because “there's no point in kind of creating a huge social mobilization strategy in a district to engage mothers and convince them to allow their kids to be vaccinated if the problem is, in fact, service delivery.”

Strong political leadership, including at the district levels, for example, is equally crucial.

But international donors also need to stay committed until polio is finally wiped out globally. At present, GPEI’s plan to 2023 has a funding gap of $3.27 billion, which it hopes will be filled at the polio pledging summit in Abu Dhabi on Nov. 19.

That money does not yet include funding for inactivated polio vaccine. Funding for that is expected to come from Gavi’s replenishment next year.

“We need the international community to stay engaged, to make sure that we have the resources to finish the job,” he said.

At the World Polio Day parliamentary event last week in Canberra, Chris Maher, senior adviser to the WHO director-general, said global efforts to eradicate polio have benefitted from the support of the Australian government, agencies, and people, and he hoped it would continue.

“We would, of course, love it if you were to come in November to the pledging event and give us a nice fat check — we would be delighted,” he said.

“But, most importantly, we need you to come to the event and show that you are still present, are still part of the initiative, and still behind what’s happening to finish polio in Australia,” he added.

The billion-dollar question, however, is when will the world finally reach polio eradication. Is it happening in 2020? WHO’s Rosenbauer said from a technical point of view, there’s no reason polio should persist anywhere beyond 2020. The world has the tools and the technical know-how to beat the disease.

“The problem where it gets complicated is if you don't vaccinate children,” he said. “So that's the big question. Is Pakistan going to be able to raise its game to such a degree that really all children are reached? … It's a political and societal decision how quickly now we will eradicate this disease,” he said.