The global polio vaccination programme has confined the virus to just seven countries in Africa and Asia, with hopes to wipe out these pockets as early as next year, and to certify the world polio-free by 2007.
But a new Russian study suggests that the disease could resurface as vaccination rates drop off. This is because the common oral polio vaccine (OPV) contains a live virus that can mutate into a disease-causing form. The researchers warn that if countries stop using OPV, mutant virus might spread into unprotected populations.
Experts are aware that OPV must be phased out carefully. The new research will add to the debate over how best to wind up oral polio vaccination once global eradication is complete.