Thankfully, not many researchers nowadays have seen what I once saw: a child in an iron lung, afflicted by what was likely the last polio case in Bangladesh.
We are very close to wiping out this childhood disease, but we’re not finished yet. At this critical time in polio eradication, to rest or slow our efforts, assuming inevitable success, would be morally unjust and scientifically unwise. That’s why our work at PATH is marked by a forward-thinking approach to ensure that we have the tools we need to not only achieve polio eradication, but also to be extremely vigilant and constantly guard against its comeback.
Novel vaccines for the post-eradication era
PATH and partners are in the early stages of testing two novel oral polio vaccine candidates against type 2 polio (nOPV2). You may wonder: If we have effective vaccines that have brought us this far toward ending polio, why are new vaccines part of our long-game strategy?
An Achilles’ heel in currently available oral polio vaccines (OPVs) is one of our challenges before the finish line. OPVs have had an invaluable impact in driving down polio cases, and they remain the best tool for outbreaks because they prevent person-to-person disease transmission. But the current OPV can, in rare cases, revert to its virulent form, shed from a person, and circulate in the community. In the post-eradication era, we can’t risk seeding future outbreaks. If successful, nOPV2 could be deployed during an outbreak—with less likelihood of introducing any lurking strains that could compromise the elimination of polio.
Inactivated polio vaccine (IPV) is the vaccine that will continue to be used as a safeguard in the years after polio eradication. It is highly effective in protecting an individual who receives the vaccine, but IPV’s Achilles’ heel is that it doesn’t stop person-to-person disease transmission. Because of this, IPV is ideal in areas where there’s very little polio, but OPV is ideal in areas with high disease burden or in an outbreak. OPV stops person-to-person transmission because it induces gut immunity, which halts the pathway of how polio spreads. Unfortunately, OPV poses challenges for eradication when in those rare instances it sheds and reverts to its virulent form in the environment.
But what if there was a way we could tweak IPV so that it induces gut immunity like OPV—and thus prevent transmission? We are researching adding a component to boost IPV performance—called an adjuvant—that would induce the gut immunity necessary for stopping disease transmission. If successful, we would have a “super” vaccine that would work in all disease burden settings without the OPV-related shedding risks.
Beyond vaccines: preparation and vigilance
The global polio vaccine community has agreed upon special set of safety guidelines on proper handling and containment of poliovirus, which requires preparation. Do we have enough facilities that meet the global containment and safety requirements? Do they have enough resources for the testing research they’ll need? Our team is working with facilities to assess their needs and build their capacity. Other teams within PATH are working on surveillance tools and new vaccine delivery technologies that are easy to deliver and won’t require cold chain.
I still receive messages from polio survivors I met during my PhD research who ask me how I’m currently contributing to the eradication effort; they don’t want to see anyone else go through what they went through. I feel optimistic not just because of the remarkable progress we’ve made, but also because of so many promising tools in the pipeline to get the final edge against polio and keep the upper hand for good.
- Rahnuma Wahid is a senior technical officer with PATH’s Center for Vaccine Innovation and Access.