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Comparison of Polioviruses Used in Vaccines Finds Newly Developed One Is More Stable

Researchers from the Center for Vaccine Innovation and Access at PATH examine the genetic and phenotypic stability of two different polioviruses used in vaccines. While vaccination with the Sabin oral poliovirus vaccine (OPV) provides immunity against the virus, that virus can, on rare occasions, revert and regain virulence to cause infections within low-immunization populations. In a new The Lancet Microbe study, researchers used data from two recent clinical trials in Panama to compare the viruses shed by individual immunized with monovalent OPV2 (mOPV2) or novel OPV2 (nOPV2) — nOPV2 was designed to provide similar protection as mOPV2 but with lower risk of reversion. In their analysis, the researchers found that the site where most attenuation occurs, domain V, of nOPV2 was more genetically stable than that of mOPV2. Further, mice given shed nOPV2 were less likely to develop paralysis than those given shed mOPV2. "While this vaccine is currently being deployed under an emergency use listing, the data on the genetic stability of nOPV2 will support further regulatory and policy decision-making regarding use of nOPV2 in outbreak responses," the PATH team adds.