Originally Posted by N1120A

Whether it is required for travel TO a country is only part of the equation. Some countries - South Africa and Australia are particularly tough on this - require it if you have been to countries that have yellow fever in them, even if it is confined to certain regions. So, for example, if you do a trip to Tanzania and South Africa, you MUST get your yellow card in order to go to South Africa second. Similarly, if you go to Kenya before Tanzania, you MUST have your yellow card.