There is no risk of yellow fever in Costa Rica. However, the government of Costa Rica requires proof of yellow fever vaccination if you are arriving from a country with risk of yellow fever—primarily from some countries in South America or sub-Saharan Africa. If you will travel directly to Costa Rica from one of these countries, you will need to show proof that you received the Yellow Fever vaccination 10 days prior to your travel. Some exceptions exist. Find more information here: http://www.costarica-embassy.org/index.php?q=node/109
