Anecdotes tell us what the data can’t: Vaccinated people appear to be getting the coronavirus at a surprisingly high rate. But exactly how often isn’t clear, nor is it certain how likely they are to spread the virus to others. Though it is evident vaccination still provides powerful protection against the virus, there’s growing concern that vaccinated people may be more vulnerable to serious illness than previously thought. There’s a dearth of scientific studies with concrete answers, leaving public policy makers and corporate executives to formulate plans based on fragmented information. While some are renewing mask mandates or delaying office reopenings, others cite the lack of clarity to justify staying the course. It can all feel like a mess. “We have to be humble about what we do know and what we don’t know,” said Tom Frieden, a former director of the Centers for Disease Control and Prevention and the head of the nonprofit Resolve to Save Lives. “There are a few things we can say definitively. One is that this is a hard question to address.” Absent clear public health messaging, vaccinated people are left confused about how to protect themselves. Just how vulnerable they are is a key variable not just for public health officials trying to figure out, say, when booster shots might be needed, but also to inform decisions about whether to roll back reopenings amid a new wave of the virus. On a smaller scale, the unknowns have left music lovers unsure if it’s OK to see a concert and prompted a fresh round of hang-wringing among parents pondering what school is going to look like.