The campaign will target children under the age of five in 19 countries
A campaign has been launched to eradicate polio in west and central Africa, targeting 85 million children.
Some 400,000 health workers and volunteers will go from door-to-door in 19 countries, giving oral polio vaccine to children under the age of five.
Africa has made significant progress in the fight against polio, which attacks the nervous system, but the virus has still not been stamped out.
Previous efforts at eradication failed as too few children were vaccinated.
The effort is a joint campaign by the Red Cross and United Nations.
Many analysts believe the key to its success lies with Nigeria.
In the past, campaigns in the north of the country were met with suspicion by religious leaders, some of whom even suggested the vaccinations were an attempt to spread sterility and HIV.
But religious groups are now showing support for vaccination drives, and correspondents say there is optimism that the debilitating, sometimes fatal, virus can be eradicated.