If you had visited the University of Antwerp, Belgium, in the summer of 2017, you’d have seen something highly unusual: two massive rectangular boxes spanning the length of several parking spaces.
From the outside, the boxes would have seemed nondescript—like shipping containers with windows. But if you were a participant in the groundbreaking clinical trial they housed, those boxes would have been your home for almost a month.
Named Poliopolis by researchers, the boxes formed a self-contained village where two sequential groups of 15 volunteers agreed to live for 28 days. These individuals were taking part in an important scientific effort: the first-in-human, phase 1 clinical trial of two novel oral polio vaccine (nOPV2) candidates.
The candidate vaccines hold promise against type 2 poliovirus. The first group received one candidate; the second received the other.
It was the first study on new strains of oral polio vaccines to get this far in more than half a century.
The rules of containment
The University of Antwerp, a partner in the nOPV2 project coordinated by PATH, put this special infrastructure in place to satisfy World Health Organization guidelines. Activities involving any form of live poliovirus type 2 must exercise extreme caution to prevent its release into the environment. Though the facility was called a “container village,” it functioned more like an island to minimize the risk of transmission to the outside world.
Oral polio vaccines are created with an attenuated version of the live virus. Because the vaccine is given orally, this weakened virus passes through and replicates in the intestinal tract to induce immunity. It is subsequently “shed” (a euphemism for its exiting the body in fecal matter).
In areas of inadequate sanitation, this excreted vaccine virus can spread into the surrounding area and be transmitted, at first offering protection through what is known as passive immunity. But it can eventually mutate. When this happens, the virus can become virulent—changing to a form called circulating vaccine-derived poliovirus, or cVDPV. Tragically, these circulating strains have caused rare cases of polio disease in areas where not enough people are vaccinated.
For this reason, Poliopolis had an unconnected, free-standing plumbing system that enabled researchers to decontaminate waste before it ever reached the environment.
The results, published in the Lancet, provided key safety and effectiveness data, which supported the advancement of both candidates into the next round: phase 2 trials.
“Novel” solutions to current vaccine limitations
The staggering advances we’ve made against polio would not have been possible without the current oral polio vaccine. This vaccine, a groundbreaking accomplishment in its era, has brought us tantalizingly close to the dream of making polio the second disease—after smallpox—to be eradicated.
Yet a new vaccine is needed to snuff out the last cVDPVs. Early research suggests that the new oral vaccine strains are more genetically stable than the current form, but with the same protective benefits.
Phase 2 trials are currently underway. This time, thanks to the encouraging results from the phase 1 trial, the volunteers can come and go as they please.
One day, with continued innovation and investment, the same will not be said for polio.