Vaccine derived poliovirus circulating in Lao People's Democratic Republic


Lao is affected by a circulating vaccine-derived poliovirus type 1 (cVDPV1) outbreak.

Fatal case associated with vaccine derived polio virus – September 2015
An 8 year old boy from the district of Bolikhan, in Bolikhamxay Province developed paralysis in September and the boy died shortly after onset of paralysis. WHO received laboratory confirmation in October that the infection was caused by circulating vaccine-derived poliovirus type 1 (cVDPV1).

Genetic sequencing of the virus suggests that it has been circulating in the area for more than two years. The boy was from a district that has chronically low immunisation rates: reported coverage with 3 doses of oral polio vaccine (OPV) was of 40% to 66% between 2009 and 2014; and 44% in 2015 to date.

Lao’s last case of indigenous wild poliovirus was reported in 1993.

Circulating vaccine-derived polioviruses (cVDPVs) are rare but well-documented strains of poliovirus mutated from strains in oral polio vaccine (OPV). They can emerge in some populations that are inadequately immunized.

Because of relatively limited travel to and from this area and the planned immunization activities, the World Health Organization (WHO) assesses the risk of international spread of the cVDPV1 from Lao to be low.


  • WHO's International Travel and Health recommends that all travellers to polio-affected areas be fully vaccinated against polio. 
  • Travellers from Ireland to polio infected countries, even if they previously received three or more doses of OPV or IPV, may also need a booster dose of polio vaccine (such as Tdap/IPV) before travel and should consult their travel health clinic or GP.

For more information

WHO Disease Outbreak News: 

NIAC guidance on polio vaccination: