Polio research gives new insight into tackling vaccine-derived poliovirus

A vaccine-derived strain of poliovirus that has spread in recent years is serious but it can be tackled with an existing vaccine, according to a new study published today in the New England Journal of Medicine.

Vaccine-derived polioviruses can emerge on rare occasions in under-immunised populations, when the attenuated virus contained in a vaccine mutates and recombines with other viruses, to create a circulating vaccine-derived strain.

The researchers behind today's study say their findings highlight the importance of completing polio eradication. They also say that should wild-type poliovirus be eradicated, routine vaccination with oral polio vaccines will need to cease, in order to prevent further vaccine-derived strains of the virus from emerging.

The study was carried out by researchers from the Medical Research Council Centre for Outbreak Analysis and Modelling at Imperial College London, working with the government of Nigeria and the World Health Organization (WHO) research teams.

Poliovirus is highly infectious and primarily affects children under five years of age. Around one in 200 of the people infected with polio develop permanent paralysis, which can be fatal.

Polio was virtually wiped out by the early 2000s following a major vaccination drive by the Global Polio Eradication Initiative, but since then the number of cases of paralysis reported has plateaued, remaining roughly constant at between 1,000 and 2,000 each year from 2003 to 2009, dropping only recently in 2010.