New cases of polio linked to the oral vaccine have been reported in four African countries and more children are now being paralysed by vaccine-derived viruses than those infected by viruses in the wild, according to global health numbers.
The World Health Organization (WHO) and partners identified nine new cases caused by the vaccine in Nigeria, the Democratic Republic of the Congo, Central African Republic and Angola last week. Along with seven other African countries with outbreaks, cases have also been reported in Asia. In Afghanistan and Pakistan polio remains endemic, and in Pakistan officials have been accused of covering up vaccine-related cases.
The onset has been caused by a type 2 virus contained in the vaccine. Type 2 is a wild virus that was eliminated years ago, but in rare cases the live virus in oral polio vaccines can mutate into a form capable of igniting new outbreaks of the disease.
A report released earlier this month by the Independent Monitoring Board, which independently assesses the GPEI’s work and progress toward polio eradication, claimed that the vaccine-derived virus was causing an uncontrolled outbreak in west Africa. The report found “the strategy is already failing badly on the goal of reducing, and ultimately eliminating, vaccine-derived polioviruses” and argued that new strategies are needed to tackle the polio epidemic.