Info from kenya airways site
http://www.kenya-airways.com/home/information_and_services/plan_your_trip/travel_information/health_information/default.aspx
Vaccination against Yellow Fever, if arriving in Kenya within
6 days after leaving or transiting countries with infected
areas.
Exempt from Yellow Fever vaccination:
- Children under 1 year.
- Those not leaving the airport in Kenya.
- Those not leaving the airport in the countries concerned.
Recommended:
- Vaccination against Yellow Fever for all passengers visiting
any area outside the main cities in Kenya.
- Malaria prophylaxis. Malaria risk - mainly in the malignant
(P. falciparum) form - exists throughout the year in the
whole country. There is normally little risk in the city of
Nairobi and in the highlands (above 2500 m.) of Central,
Rift Valley, Eastern, Nyanza and Western Provinces. P.
falciparum highly resistant to chloroquine and resistant to
sulfadoxine/pyrimethamine reported. Recommended prevention:
IV. The Kenyan Ministry of Health expects travel
representatives to inform their clients about Malaria risk
and recommend them to take the necessary antimalarial
measures.
Warning:
- Passengers not holding valid Yellow Fever certificate, if
required, are subject to quarantine.