Report offers harsh verdict on global polio vaccine switch

摘要

Something momentous happened in the history of polio eradication in April 2016: Over a period of 2 weeks, 155 countries and territories started to use a new version of Albert Sabin's classic oral polio vaccine (OPV) that no longer protected against one of the three types of poliovirus. Type 2 virus had been eradicated by then, and the only remaining type 2 polio cases were touched off by the live virus in the vaccine itself. Dropping the type 2 component from the vaccine would end those cases as well, the thinking went.