Infant among new cases of vaccine-derived polio reported in Laos

Two additional cases of circulating vaccine-derived poliovirus type 1 have been reported in Laos, amid ongoing outbreak response activities, according to WHO.

“Since the detection of the first confirmed [circulating vaccine-derived poliovirus type 1 (cVDPV1)] in Laos, outbreak response activities have been conducted nationwide,” WHO officials wrote in a news release. “The national Emergency Operations Centre has been activated to coordinate response efforts and a polio outbreak response plan was drafted. Enhanced surveillance is occurring throughout the country, including daily zero-reporting of [acute flaccid paralysis (AFP)] cases.”

The newly reported cases include a boy aged 14 months and a man aged 40 years, both from the same district in Xaisomboun Province. The infant developed a fever that progressed to hyporeflexia and asymmetric paralysis in both legs within 2 days. Vaccine history indicated that the child received three doses of oral polio vaccine (OPV), and the child tested negative for any poliovirus. After the child’s asymptomatic sister tested positive for vaccine-derived poliovirus type 1 (VPDV1), health officials reported the boy’s case as VPDV1, based on the association with a positive contact and the proximity to another confirmed case within the same district.

The second case in the adult was reported after he presented with hyporeflexia and symmetric paralysis in both legs, but without fever or pulmonary issues. Vaccine history also revealed that the man never received any OPV; however, he tested positive for VPDV1.

A 6-month vaccination campaign, started in October, is currently underway in Laos, through which 10 million doses of OPV will be administered to children aged younger than 15 years by March.

WHO’s International Travel and Health along with the CDC recommend that all travelers to Laos be fully vaccinated against polio. Further, the CDC recommends that adult travelers receive a single lifetime booster dose of polio vaccine.

“Active case finding is ongoing in high-risk districts, including retrospective review of hospital and health center records,” WHO officials said in the release. “To ensure the success of supplementary immunization activities, emergency risk communications and social mobilization activities, including training of mobilizers and information sessions to build trust and address barriers to immunization, are being conducted.”