Circulation of polio vaccine-derived strains in unvaccinated populations

A global public health effort to eliminate all cases of polio infection around the world has reduced the number of annual diagnosed cases from the hundreds of thousands to 37 confirmed cases in 2016 and 11 in 2017. However, the live polio vaccine strain can mutate (although rarely) and cause sporadic paralyzing polio-like infection. The mutated vaccine strains, known as cVDPV, usually cause clinical illness in populations where the level of immunity to this virus has decreased due to lack of sustained polio vaccination programs, especially in difficult to access areas.

During 2017, two new cVDPV outbreaks were detected in the Democratic Republic of the Congo and one in Syria. The cVDPV strain emerged in Laos, Nigeria and Pakistan in 2016.

Advice

Travellers in any country that reports cases of polio can reduce their risk of exposure to poliovirus by ensuring that their childhood vaccinations, including polio, are up-to-date prior to travelling. Travellers who are visiting infected areas for more than 4 weeks should receive an additional dose of oral polio vaccine or inactivated polio vaccine within 4 weeks to 12 months before travelling.