What’s the shortest way to the next medical breakthrough? Open borders. A group of medicine professors at Stanford University is clear that restricting immigration is bad for our health. In the past, collaboration among scientists from around the world made vaccines for polio and smallpox possible and enabled countries to develop crops capable of feeding their populations. Moreover, as the spread of Zika and Ebola has demonstrated, diseases know no boundaries. Fighting and curing them requires cross-border collaboration. Scientific progress is built on the robust sharing of information and ideas.