Here’s how Walensky defended the decision to not recommend rapid tests, to CNN:

We opted not to have the rapid test for isolation because we actually don’t know how our rapid tests perform and how well they predict whether you’re transmissible during the end of disease. The FDA has not authorized them for that use. We don’t know how they perform. So what we said was, well, if you got a rapid test at five days and it was negative, we weren’t convinced that you weren’t still transmissible. We didn’t want to leave a false sense of security. We still wanted you to wear the mask. And if it was positive, we still know the maximum amount of transmission was behind you. We still wanted you to wear a mask. And given that we were not going to change our recommendations based on the result of that rapid test, we opted not to include it.

This is nonsensical on a few levels. The Food and Drug Administration doesn’t have to greenlight every single specific use of a medicine or a test for doctors to use it. We allow Botox for migraines and aspirin for strokes, for example. And while it’s true that we don’t know with absolute mathematical certainty how well rapid antigen tests detect contagiousness at each stage of COVID, that’s hardly a justification for tossing them aside. If a patient tests positive, it means they are still producing lots of the virus, which is a very good reason to worry that they could still be infectious to others. Sure, perhaps someone could test positive without being contagious—but it seems worth erring on the side of having people stay isolated, versus sending them out into the world with a mask. “They’re used in the U.K. and all the other countries that have relied on rapid tests for well over a year, just for this reason,” says Topol. “They have a protocol for self-isolation until your rapid tests convert into negative. So to question that is preposterous, because that’s been well established and validated.”