I posed this question to Chelsea Boyd, a research associate in harm reduction at the libertarian R Street Institute with a master’s in epidemiology. “Simply from a logistics perspective, I’m not sure how a large country would manage to process certificate requests and validate test results with any measure of speed, accuracy, or equity,” she said. Something may be feasible in Germany — with a quarter of the United States’ population in a 27th of the territory — but impossible here.

Yet bureaucratic limitations weren’t the only issue Boyd raised. Another is the nature of antibody testing itself, coupled with what we simply don’t know about COVID-19 immunity. Antibody tests don’t “differentiate between a remitted infection and an active infection,” she noted, and home testing (like that planned in Germany) is “generally considered less reliable than lab-confirmed testing.” That’s not to say it’s worthless, only that user error and test precision are real concerns (compare, for example, home pregnancy tests to those done by a doctor or midwife).

Furthermore, though “evidence strongly suggests that after a person recovers from COVID-19 they are immune to reinfection, at least in the short term,” Boyd told me, we don’t know that for certain or if the short term is weeks, months, or years. And immunity certificates “are meaningless,” she continued, “if COVID-19 immunity isn’t complete or lasting.”