The art of ending – how to best eradicate polio

As one of the most prominent expert on polio, Jacob John and his colleagues write, vaccine safety is usually defined as the absence of serious adverse events in the vaccine recipient, yet the continued use of oral poliovirus vaccine (OPV) has quietly stretched that definition by tolerating vaccine‑associated paralytic polio (VAPP) in both vaccinees and their contacts at low but predictable frequencies. The authors argue that this permissive framing has allowed the world to persist for decades with a live vaccine that not only causes VAPP but also seeds circulating vaccine‑derived polioviruses (cVDPVs), which now generate hundreds of paralytic cases each year and have become a major obstacle to eradication. They emphasise that OPV strains were never truly “attenuated” in the modern genetic sense but are low‑fitness derivatives of wild viruses that retain residual neurovirulence and transmissibility, making contact‑VAPP and reversion to wild‑like behaviour biologically inevitable when these strains replicate...