In response to a polio outbreak originating in Nigeria, an eight-country synchronized vaccination campaign in West Africa kicks off on 27 February 2009. Nigeria and seven of its neighbours will immunize more than 53 million children over four days and again in late March. More than 162 000 vaccinators will implement the campaign in these countries.

With 50 cases of type 1 polio reported in Benin, Burkina Faso, Côte d’Ivoire, Ghana, Mali, Niger and Togo, this mass immunization campaign aims to tackle the virus in two rounds, the first from 27 February–2 March and the second from 27–30 March. Type 1 poliovirus is the more dangerous of the two wild poliovirus strains, due to its higher paralytic attack rate and propensity for greater geographical spread.