Van Damme P, et al. – Researchers assessed the safety and immunogenicity of two novel monovalent oral type-2 poliovirus (OPV2) vaccine candidates that are genetically more stable than existing OPVs, with a lower risk of reversion to neurovirulence. They also assessed the presence and extent of fecal shedding, and the neurovirulence of shed virus. The study sample consisted of 30 eligible participants who were divided into 2 equal groups. Participants were given a single dose of each vaccine candidate (candidate 1, S2/cre5/S15domV/rec1/hifi3; or candidate 2, S2/S15domV/CpG40), and were monitored for adverse events, immune responses, and fecal shedding of the vaccine virus for 28 days. The incidence and type of serious and severe adverse events, the proportion of participants demonstrating viral shedding in their stools, the time to cessation of viral shedding, the cell culture infective dose of shed virus in virus-positive stools, and a combined index of the prevalence, duration, and quantity of viral shedding in all participants comprised the primary outcome. Overall, in this double-blind, single-center, phase 1 trial, no intolerability or serious adverse events were reported during the study course. Both OPV2 candidates were found to be safe and immunogenic in injected inactivated polio vaccine-immunized adults, and study findings support the further development of these vaccines for potential use in maintaining global eradication of neurovirulent type-2 polioviruses.