Earlier this year, the World Health Organisation (WHO) updated its stance on booster vaccinations for yellow fever, stating that a single vaccination should be considered effective for life instead of ten years as previously.
Pending the update of WHO International Health Regulations announced for 10 July 2016, vaccination practices and requirements are in a state of flux with some countries considering that yellow fever vaccinations require ten year boosters and asking seafarers to provide vaccination certificates with ten year validity, some still vaccinating local populations every ten years but recognising life-time validity for seafarers, and others recognising lifetime validity for both their own vaccinations and for those of visitors to their country.