To stay in Kenya you are not obliged to any vaccination.
Yellow fever for years does not manifest itself in the territory since 1989 and is no longer required it. It is only required for those coming from countries where it is mandatory and still present, such as Tanzania.
Malaria speak extensively in articles below.
In some areas of Kenya, however, very little frequented by foreign travelers, there may be isolated outbreaks of cholera, especially in the Lake Victoria area.
For Western man, the risk of contracting some gastrointestinal viruses, like jardia, amoebas and intestinal parasitosis.
As in many other countries around the world, it is recommended to wash the foods to be eaten uncooked (fruits and vegetables) and not to drink the tap water.
Pay attention to the foods consumed in the street stalls, fish and raw shellfish, if not blatantly just caught.
Even the ice in the local Kenyans can be done with tap water, best to avoid (or ask).
Some health warnings present in the draw by news network of twenty or thirty years ago. Meanwhile kenya has evolved.
Regarding the on-site treatment, the ideal is to get in a pharmacy and realize how many "corrective in the running" can be found for any identified pathology.
For example, as regards malaria, now all local pharmacies selling products based on artemisinin, which act "the day after" and make the prophylaxis, that is harmful to his health, now useless.