What type of vaccination is needed to enter Costa Rica?

Be aware that even if your were only transiting through any one of the following countries, Costa Rican authorities will require a yellow-fever vaccine certification: Angola, Benin, Burkina Faso, Cameroon, Democratic Republic of Congo, Gabon, Gambia, Guinea, Liberia, Nigeria, Sierra Leon, Sudan, Bolivia, Venezuela, Brazil, Peru, Colombia, Ecuador and Guyana.