Yellow fever certificate requirements depend on where you are travelling from and which countries you are entering, so the answer is not a simple yes or no for everyone.

Uganda, Kenya, Rwanda, Tanzania and Burundi are all within the yellow fever endemic zone, and if you are arriving directly from a country outside that zone with no yellow fever risk, such as the UK, most of Europe, the UAE or the US, you may not be strictly required to show a certificate on entry, though requirements can be interpreted differently by individual officers and do get updated, so always check current requirements for your specific nationality and route before travelling.

Where it becomes essential rather than optional is if you are arriving from, or have transited through, any country with yellow fever risk. This is the situation many regional travellers fall into without realising it, for example flying from Kenya into Rwanda, or from Tanzania into Uganda. In these cases, a valid certificate is checked and required, and without one you risk being vaccinated on the spot at the border, which is neither pleasant nor how you want to start a holiday, or in some cases denied entry.

Given the East African Tourist Visa explicitly allows movement between Kenya, Rwanda and Uganda, and most itineraries in the region involve crossing at least one border, we recommend every visitor to East Africa gets vaccinated and carries the certificate regardless of their first entry point. It removes any ambiguity, protects you medically since yellow fever is a genuinely serious disease present in parts of the region, and avoids any risk of a difficult conversation at immigration.

The vaccine needs to be administered at least ten days before travel to be valid on your certificate, so this is not something to leave until the airport. Book it with plenty of lead time.