The presidents of Benin and Nigeria have helped launch a program to vaccinate 40 million children in the region against polio.
Benin's President Mathieu Kerekou and his Nigerian counterpart Olusegun Obasanjo met on their shared border Sunday to drop vaccine into babies' mouths to start the campaign.
The World Health Organization is backing the effort aimed at reversing a surge in polio cases which started in Nigeria.
In late 2003, Islamic leaders in northwestern Nigeria suspended immunizations, claiming the WHO had supplied a vaccine that would cause sterility. Health officials denied the claim.
The WHO said the ban caused the number of polio cases in West Africa to double last year.
Nigerian leaders last year agreed to resume anti-polio efforts, using a different vaccine.