Originally Posted by
B747-437B
I have a 2015 vaccination which has been endorsed with a "Valid For Lifetime" stamp in 2020. It has been accepted in both Kenya and Tanzania without any comment.
My wife has a 2010 vaccination which has been questioned in Tanzania, on the basis that only vaccines issued after 2016 have lifetime validity and not those before. However, if she got the same "Valid For Lifetime" endorsement I did, it would be fine.
TL;DR - they make it up as they go.
My wife had that issue. We received our YF inoculations from a travel medicine clinic chain. She simply went back and they re-issued her YF yellow book with a new one with all the relevant information (the original vaccine batch & date and a stamp indicating it as a WHO lifetime effective inoculation), This clinic issues the YF vaccine data in a separate yellow book. No issues after several trips through ADD and othe airports in listed YF countries.