1. Global Immunization Division, U.S. Centers for Disease Control and Prevention, Atlanta, GA 30329, USA
2. Epidemic Intelligence Service, U.S. Centers for Disease Control and Prevention, Atlanta, GA 30329, USA
3. Expanded Programme on Immunisation, Disease Control and Prevention Department, Public Health Division, Ghana Health Service, Accra P.O. Box M 44, Ghana
4. Neglected Tropical Diseases Control Programme, Disease Control and Prevention Department, Public Health Division, Ghana Health Service, Accra P.O. Box M 44, Ghana