Travel restrictions as a disease control measure: Lessons from yellow fever.

Travel restrictions have become a common disease control measure during the 2019 Coronavirus disease pandemic (COVID-19). Measures have ranged from quarantines when entering a country to outright travel bans. Yet more widespread travel restrictions in the form of country vaccine entry requirements have been in place for a long time for another disease - yellow fever. We track the historical underpinnings and policy developments that have led to stringent vaccine entry requirements today. We also discuss the political issues raised by health measures imposed on borders and discuss the reasons behind some clear regional differences. Almost no European countries currently have vaccine entry requirements, while at the other end of the spectrum, the majority of countries in the African region do, making vaccine entry requirements a global south phenomenon. We argue that vaccine entry requirements should be reassessed in the future as an underused public health tool, likely to become increasingly common. Vaccine entry requirements have proved effective in controlling the international spread of yellow fever but more can be done to ensure better use of this measure. Caution is needed due to the close links between public health and politics, evident since the first travel restriction in quarantines.