Polio eradication, cessation of vaccination and re-emergence of disease

The poliovirus eradication programme coordinated by the World Health Organization mainly involves immunization with a live attenuated vaccine. Only six countries - India, Pakistan, Afghanistan, Egypt, Nigeria and Niger - still have endemic poliovirus. To tackle recent outbreaks in India and Nigeria, eradication strategies have been refocused. It was hoped that complete eradication of wild-type poliovirus would be achieved by the end of 2003, but during 2004 there have been setbacks to polio immunization in Nigeria, and the number of poliomyelitis cases has increased. It still seems possible that the virus could be eradicated - but should vaccination continue when that goal has been achieved?