How accurate are at-home COVID tests amid Omicron spike?

President Biden today tried calming nerves about the spread of the Omicron variant over Christmas. The administration is mobilizing 1,000 military medical personnel in case of staffing shortages at hospitals around the country, ramping up FEMA-run pop-up vaccination clinics for booster shots, and purchasing half a billion at-home rapid COVID tests to send to any American who asks for one. Deliveries will begin in January.

It’s an about-face from earlier this month when White House Press Secretary Jen Psaki dismissed the notion of mailing millions of tests to Americans. That was before Omicron’s rapid and alarming spread.

In just three weeks, Omicron has already become the dominant variant here, accounting for more than 70% of new cases, according to the CDC.

Susan Butler-Wu, a clinical microbiologist and professor at USC’s Keck School of Medicine, says people interested in at-home tests can request them online, but other details are unclear.

The new policy is a shift from a previous Biden administration announcement that would require insurance companies to reimburse the costs of the tests.

Butler-Wu points out that there needs to be better education around the use and efficacy of the at-home antigen tests.

She says these tests have typically performed well during the first week of symptoms, but stresses that a negative test does not rule out a COVID infection.

“If it's negative, it doesn't mean that you couldn't still have COVID because any test is just a snapshot of what's happening up your nose at that moment. And certainly with Omicron, what we're seeing is people can test negative and then test positive later.”

She says it’s important to test multiple times if there is cause for concern, because as time goes on, more virus particles are replicated in the body and therefore can be detected more easily.

But because of how little is known about Omicron, Butler-Wu says that antigen tests are not a substitute for vaccinations or boosters, and people should be vigilant about taking all safety precautions, like wearing masks, ventilating spaces, and not assuming that any little sniffle is just a cold.