Vaccination certificates are COVID tests are no longer mandatory, but if you are presenting flu-like symptoms you will need to do either a PCR or an Antigen test and self-isolate if testing positive.
It is better to obtain an eVisa before your date of travel. Please print the evisa in advance, otherwise you may print at the border for a fee.
Kenya: https://evisa.go.ke/evisa.html
Tanzania: https://eservices.immigration.go.tz/visa/
You may be required to present a yellow fever vaccincation certificate. We advise you check your own nationalities traveling instructions.