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Vaccine-derived poliovirus emerges in Laos
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WHO has reported three cases of vaccine-derived poliovirus circulating in the Bolikhan district of Laos, according to a press release.
“Circulating vaccine-derived polioviruses are rare but well-documented strains of poliovirus mutated from strains in the oral polio vaccine,” WHO wrote in the release. “They can emerge in some populations that are inadequately immunized.”
Between 2009 and 2014, only 40% to 66% of infants in the Bolikhan district received all three doses of oral poliovirus vaccine. In addition, the most recent case of indigenous wild poliovirus in Laos occurred in 1993.
“Ending polio for good requires eliminating both wild and vaccine-derived polio,” WHO wrote in the release. “And, due to the small risk of circulating vaccine-derived polioviruses, use of the oral polio vaccine must be stopped to secure a lasting polio-free world.”
WHO has already planned to administer the trivalent oral polio vaccine between October 2015 and March 2016, with 8.6 million doses going to children younger than 15 years. However, in April, WHO plans to switch from trivalent to bivalent vaccine to reduce the risk of circulating vaccine-derived poliovirus. Eventually, WHO plans to switch from oral vaccine to inactivated vaccine, which cannot cause circulating vaccine-derived poliovirus.
“It is important that all countries, in particular those with frequent travel and contacts with polio-affected countries and areas, strengthen surveillance for acute flaccid paralysis cases in order to rapidly detect any new virus importation and to facilitate a rapid response,” WHO wrote in the release. “Countries, territories and areas should also maintain uniformly high routine immunization coverage at the district level to minimize the consequences of any new virus introduction.”
WHO’s International Travel and Health still recommends that all travelers to areas affected by polio should receive the polio vaccine. In addition, they recommend that residents from infected areas should receive an additional dose of oral or inactivated vaccine within 4 weeks to 12 months of travel.