Hi,
In my experience, having been to Zambia, Zimbabwe, Nigeria, Senegal and South Africa, some countries can require the following:
- Yellow fever vacation
- An international vaccination booklet (issued where you get vaccinated, not by WHO), certifying that you have had a yellow fever shot.
IIRC, Zambia actually asked to see my vaccination booklet, the others did not. The booklet does not need to carry any other information.
Cheers,
GenevaFlyer