Beginning this week, guarded vehicles loaded with the first Covid-19 vaccine authorized in the United States are fanning out to hospitals across the country. In vaccine prioritization protocols health care workers, along with nursing home residents, make up phase “1a” – those who are first in line to be vaccinated. While much attention has been paid to who should come next, less is known about how hospitals are allocating vaccine doses among their staff. For many medical centers, the first shipments will only be enough to vaccinate a fraction of their workers. Who goes first within the “1a” category, and how are such decisions made?