https://www.ivisa.com/south-africa-visa

Usually, it's wise to get vaccinated and receive a valid Yellow Fever certificate a minimum of 10 days ahead of your travel if you are going to or passing through a country where YFV occurs.  Make certain you're vaccinated before going into the country if you're coming from a region with yellow fever.  Africans like to travel and Kenyans aren't an exception.