1. Epidemic Intelligence Service, Centers for Disease Control and Prevention, Atlanta, Georgia;
2. Global Immunization Division, Centers for Disease Control and Prevention, Atlanta, Georgia;
3. São Tomé and Príncipe Ministry of Health, São Tomé, São Tomé and Príncipe;
4. São Tomé and Príncipe Country Office, World Health Organization, São Tomé, São Tomé and Príncipe;
5. Regional Office for Africa, World Health Organization, Brazzaville, Congo;
6. Expanded Programme on Immunizations, World Health Organization, Geneva, Switzerland