The World Health Organization (WHO)'s goal to eradicte polio worldwide suffered a blow when a death due to the vaccine was confirmed last Sept. 11 in Laos.
According to WHO, the 8-year-old child was reportedly paralyzed by polio before dying five days later. Further study of the case found that the boy was confirmed to have a vaccine-derived poliovirus.
"[The] genetic sequencing of the virus confirmed...that it is vaccine-derived and suggests that it has been circulating in the area for more than two years," WHO said in their report. The province where the boy came from was also found to have low immunization rates for several years now. Vaccination rates in the area ranged from 40 to 66 percent in the last six years.
WHO said that the Ministry of Health, in collaboration with WHO, the U.S. Center for Disease Control and Prevention (CDC), and UNICEF, had stool samples collected from the child's village and facilitated emergency immunization efforts to all adjacent areas.
The latest case in Laos is one of the new cases of polio being found this year. Last September, WHO found that two children from Ukraine have been paralyzed due to the virus.
An African 19-month-old also became paralyzed by polio. Analysis of the causative agents for all three cases found them all to be vaccine-derived.
"Circulating vaccine-derived polioviruses are rare but well-documented strains of poliovirus mutated from strains in oral polio vaccine (OPV)," WHO said. The virus also tended to thrive better in areas that are not immunized or have low immunization rates.
This means that vaccine makers and distributors will now also have to worry about vaccine-derived strains, not just the wild ones. Live OPV should be exchanged with "inactivated" vaccines (IPV), which was found to reduce the risk for acquiring vaccine-derived polio.
"Ending polio for good requires eliminating both wild and vaccine-derived polio... to secure a lasting polio-free world," the organization explained.
Thankfully, because of limited access to travel to the area, WHO believes that there is a low risk of spreading the vaccine-derived poliovirus.
Poliomyelitis is a viral disease that affects the nerves that causes paralysis of the limbs and even of breathing muscles, which causes at most 10 percent of polio-related deaths. Paralysis induced by the infection are irreversible and cannot be cured.
Photos: CDC Global | Flickr
