or more than two years, the global initiative to eradicate polio has been trying to convince companies and laboratories around the world to get rid of stored samples of an extinct poliovirus, with little success.
Thirty countries have indicated they plan to hold on to type 2 polioviruses, in a total of 99 facilities. That, health officials warn, could endanger years of efforts to stop the virus from crippling children.
“I think it’s more than what was anticipated,” said Dr. David Heymann, an infectious diseases expert who formerly ran the polio program at the World Health Organization and who currently chairs a committee established to help resolve the containment impasse.
Experts say it’s unclear why so many countries need to retain an extinct virus — and in so many locations. But they’re hoping the vote on a resolution at the World Health Assembly — the annual meeting of the member countries of the World Health Organization — will help changes at least some minds.
The resolution, which will be debated Friday or Saturday, notes “with alarm” that the containment effort is virtually stalled.
“We were making no progress,” Michel Zaffran, the WHO’s top polio official, told STAT.
When the polio eradication effort began in 1988, there were three types of polioviruses, numbered type 1 through type 3. Type 2 viruses were last seen in 1999 and were declared eradicated in 2015. (Type 3 viruses are probably gone, but the taxing technical process that an eradication declaration requires hasn’t yet been undertaken.)
This containment effort is a result of the eradication declaration, and it is a trial run for a larger containment program for all polioviruses, when the other two types are declared extinct.
The hope is that time may be coming. To date this year there have been only eight cases of paralytic polio diagnosed, in Afghanistan and Pakistan. But Zaffran has warned it’s too soon to predict this will be the year polio transmission ceases.
Limiting the number of places that work with or store polioviruses is a critical part of the polio endgame — the plan for how to keep the world safe from polio during the final stages of the eradication process and during the period after polioviruses cease circulating.
The fear is that if this dance isn’t executed correctly, polio could accidentally escape from a laboratory or be released from a vaccine manufacturing plant. That type of reintroduced virus would place the work of decades — work that has cost billions of dollars — in jeopardy.
These fears aren’t simply theoretical. Last year two employees of a polio vaccine production facility in the Netherlands were accidentally exposed to the virus; one of them was infected. In 2014, a vaccine plant in Belgium mistakenly dumped 45 liters of concentrated polioviruses into the local sewage system, which connects to the Lasne River.
Back when smallpox — which to date is the only virus causing human disease to have been wiped out — was still being battled, the plan was that eventually all samples of the virus would be destroyed. But that hasn’t happened; the United States and Russia each maintain small stores of the virus.
With polio, the plan was that after person-to-person transmission is halted, the number of places that could work with or store the virus would be limited to as few as possible. For instance, as long as the world continues to use polio vaccine, vaccine manufacturers will need stocks of polioviruses to produce them. Likewise research laboratories working to develop safer polio vaccines need viruses to pursue that goal.
There is an added complication here: In addition to the facilities that plan to retain samples of live polioviruses, there are many other laboratories that would have stored biological samples — stool and respiratory tract mucus — that may contain polioviruses. Polio containment plans refer to them as PIMs — potentially infectious materials.
Stool collections gathered when polio still circulated, or where the oral polio vaccine is used, could contain live polioviruses or the modified vaccine viruses that are used in the oral vaccine. Working with those stool samples could inadvertently release polio.
The original plan for containment was rigid and dictatorial, Zaffran acknowledged. And when the polio program reached out to other research communities to say samples that might contain polioviruses needed to be destroyed or stored in designated safe facilities, the message was not welcomed.
“The reaction was, ‘We don’t want to talk about it because it’s totally unrealistic. It’s much too demanding,”’ Zaffran explained.
The polio eradication program didn’t have the authority to demand compliance, so a few years ago it adopted a more flexible approach, and it is working on compromise approaches to help reduce the risk posed by stored biological samples.
But there still hasn’t been much headway on containment.
“Obviously we think that with a bit more encouragement and discussion, some of these research laboratories will agree that they don’t need to handle this virus,” Zaffran said. “But at the moment, there is no voluntary movement on the part of these labs. Even if they don’t do research at the moment, they hold inventories of samples which they don’t necessarily want to destroy or give away.”
He hopes the debate over the World Health Assembly resolution will make it clear to countries that holding on to type 2 polioviruses will be costly in terms of the safety measures that will be needed and the certification hurdles they will have to clear.
“But at least it will trigger a discussion on the need to first reduce the number of poliovirus essential facilities … and make sure that these poliovirus essential facilities get into the scheme of certification of their compliance with containment,” Zaffran said.
Heymann helped to write the polio endgame plan when he was at the WHO. He acknowledged the reality of the work involved in containing the viruses exceeds even his expectations.
“The endgame is very, very complex,” he noted. “And it’s more complex than was ever imaged when eradication was begun.”