The dust has now settled, and the answer as to why so many tests came up short is relatively straightforward: Many people received false-negative antigen results because this technology has always been likely to produce false negatives. Rapid tests are known to miss about 30 to 40 percent of infections compared with the gold-standard PCR method (which already isn’t perfect), even when patients are feeling sick; self-swabbing is also less accurate than professionally obtained samples. Meanwhile, multiple studies have confirmed that the current crop of rapid tests can indeed pick up the Omicron variant, and experiments with throat swabbing suggest that the technique might help a bit but isn’t a game changer. In other words, incorrect COVID-test results became more common during the Omicron surge only because COVID home testing itself became more common. Now both will be more common still.

Rapid-test advocates have long emphasized the technology’s public-health potential: Despite the fact that these affordable devices miss many cases overall, they still diagnose the majority of actively infectious people (especially with repeated testing). The widespread screening of asymptomatic people has been encouraged to help keep public gatherings safe and break chains of transmission. Under this testing model, receiving an incorrect result wasn’t crucial, because that individual was unlikely to spread the coronavirus. But things are very different in 2022: The Biden administration is in the midst of rolling out a nationwide test-to-treat program, in which local pharmacies and health centers will provide on-site testing and immediate prescriptions for anyone who turns up positive. Early-treatment options for COVID—antiviral pills such as Paxlovid and Molnupiravir, infusions such as Remdesivir and monoclonal antibodies, and hopefully other options soon—promise to blunt some of the remaining risk from the virus among unvaccinated and high-risk vaccinated people. As these treatments must be started within five to seven days of symptom onset (depending on the therapy), eligibility requires the timely receipt of a positive result—and rapid tests will be essential. So what will happen when, as one Omicron-era study found, antigen tests start missing one in four patients whose symptoms have started in the past week?