There are no compulsory vaccinations required for entry to Kenya unless you are arriving from an area infected with Yellow Fever, in which case a Certificate of Inoculation against Yellow Fever is required for all travelers older than one year.
Visitors coming from other countries in Africa where Yellow Fever may occur, including Tanzania and Zanzibar, require a Yellow Fever certificate. The other recommended vaccinations are Typhoid, Hepatitis and Polio, and anti-malarial medication is essential.
Make sure to bring your mosquito repellent, and use long sleeves and trousers during evenings/ morning times as a prevention of getting bitten. Please consult your doctor concerning vaccination prior to your journey to make sure you are fully protected.