The fine details of the FDA’s emergency use authorization, the regulatory sign-off that allows a test to be sold, are significant. Antigen tests such as this one detect viral protein and are less sensitive than the gold-standard PCR tests, which detect viral RNA. So, to gain acceptance, Abbott showed data confirming that its test was able to classify a pool of samples in nearly the same way as PCR tests of the same samples. Although its performance was impressive, the number of samples was far smaller than would be tested under normal circumstances—just 102.

Also, the FDA’s authorization allows Abbott’s test to be used only on people with symptoms of COVID-19 within seven days of the onset of their symptoms. It cannot be used to test people at any time, an approach that is often called screening. Mina said that limits the test’s potential, because it can’t be used to detect people who carry the virus but don’t show symptoms, and asymptomatic and presymptomatic people are thought to transmit a substantial percentage of infections.

Kristian Andersen, an infectious-disease researcher at Scripps Research, noted that Abbott developed an app to go along with the test that would provide proof that a person had recently tested negative. To Andersen, this is clear evidence that “Abott didn’t just have symptomatic diagnostics in mind here, but also screening of asymptomatic people.”