As the U.S. prioritizes teachers nationwide for coronavirus vaccines, states and many districts are not keeping track of how many school employees have received the shots. While vaccines are not required for educators to return to school buildings, the absence of data complicates efforts to address parents’ concerns about health risk levels and some teachers unions’ calls for widespread vaccinations as a condition of reopening schools. The number of school staff members receiving vaccinations — and refusal rates — are unclear so far in several large districts where teachers were prioritized, including Las Vegas, Chicago and Louisville, Kentucky.