Throughout the coronavirus pandemic, the US has restricted foreign travel into the country. But when that changes, the Biden administration plans to require that people are vaccinated against COVID-19. The policy is still being developed, but across the ocean, Europe is a few steps ahead: It has already established a “green pass,” so that travelers can show their vaccination status and cross borders more easily. Not all vaccines are accepted, however, even ones that have received approval from the WHO and are being used around the globe. As The World’s Elana Gordon reports, the implications of the EU’s exclusions are being felt around the world.