Assessment of shed OPV from 1-to-5 year-old children

Sabin strains used in oral poliovirus vaccine (OPV) can revert to virulence and in rare instances cause disease or generate vaccine-derived strains leading to outbreaks in areas of poor immunization coverage. A novel OPV2 (nOPV2) was designed to stabilise the viral genome against reversion and also reduce recombination events that may lead to virulent strains. In two similarly designed clinical trials, children aged 1 to 5 years were administered one or two doses of monovalent Sabin OPV2 (mOPV2) or nOPV2. Faecally shed polioviruses following a dose of mOPV2 or nOPV2 were isolated from stools meeting pre-determined criteria and assessed for nucleotide polymorphisms using next-generation sequencing.