Is Yellow Fever Vaccine Advisable While On Synthroid To An Elderly Person?

I am over 60 and have a thyroid condition (taking synthroid) and will be travelling to Kenya and Tanzania in June. I was told that the Yellow fever vaccine should not be given to people over 60 and as it is a requirement to enter the country a medical waiver would be sufficient. Does it make a difference as well when you have a thyroid condition? Is this the usual practice not to give the yellow fever vaccine to people over 60?