A rapid test for coronavirus

Is a cheap, at-home test sophisticated enough to combat COVID-19? Researchers at Harvard University and the University of Colorado Boulder think so. Using forecast modeling in a study published in Science Advances in January, they concluded that frequent rapid testing would significantly decrease COVID-19’s spread. By quickly identifying anyone carrying the coronavirus, rapid tests enable infected individuals to self-isolate before they spread the virus to others.

In one scenario the researchers modeled, when 75 percent of the population participated in rapid-test screening every three days, the infected population dropped from 4 percent to extinction in six weeks.

But while the U.S. Food and Drug Administration (FDA) issued emergency-­use authorization for the first rapid-­screening test in May 2020, over-the-counter testing today remains limited. Some researchers argue for changing that.

Although President Joe Biden recently pledged to accelerate the U.S. vaccination timeline, the coronavirus is still mutating. Some mutations could result in new viral strains that the current vaccines are not effective against. And while vaccines may soon be available to all U.S. adults, they’re still not approved for children, and 1 in 4 Americans say they won’t get the shots—all hurdles a rapid-testing strategy could circumvent.

If we can pile testing on top of vaccines and masks, we can drive this pandemic into the ground.

The rapid tests are antigen-based, meaning they detect viral proteins on the surface of SARS-CoV-2, the virus that causes COVID-19. Some medical experts are skeptical of rapid tests because they are not as sensitive as polymerase chain reaction–based tests, which are considered the gold standard. These PCR tests look for viral genetic material, so they can detect infection at the low viral loads seen very late in infection.

But multiple studies, such as a meta-analysis published in The Lancet Microbe, show that most people are only contagious during the first week of infection. PCR tests are often late to catch cases: Laboratory processing of PCR tests takes 24 hours, and sometimes results aren’t available for days due to backlogs and supply shortages. A person with a negative PCR test could contract the virus while waiting to receive test results. Worse, a person with a positive test could spread the infection to others during the lag period.

By contrast, rapid-screening tests can be taken at home and yield results in 15 minutes. While not sensitive enough to guarantee accurate diagnosis on an individual level, they are a valuable tool for decreasing the rate of spread at the community level, according to Daniel Larremore, lead author of the January study. He compares them to other types of broad safety measures: “We know that seat belts don’t provide perfect protection. But we accept that they can statistically cut down our automobile accident fatalities.”

Of the antigen-based COVID-19 tests with emergency-use authorization, only Ellume’s COVID-19 Home Tests are available without a prescription. They cost $30 each. The Biden administration’s $230 million federal contract with Ellume, signed Feb. 1, allows the company to produce 19 million tests each month with over-the-counter availability expected early this year. Abbott’s BinaxNow rapid tests cost $25 and can be purchased for at-home use with an eMed prescription.

But Larremore believes scaled-up production can drive down the cost per test to $5, making frequent testing accessible to everyone. Innova Medical Group in Pasadena, Calif., developed an at-home COVID-19 test costing less than $5. The company has exported it to 20 countries, including the United Kingdom, since the FDA hasn’t yet authorized it.

Some clinicians question the public’s willingness to participate in frequent testing. Another concern is user error. “Conducting a test on yourself can be a stressful process, and you may unknowingly make a mistake,” said Micah Bhatti, a pathologist at the University of Texas MD Anderson Cancer Center, in an online Q&A.

Mandatory PCR testing once or twice a week allowed many U.S. college campuses to return to in-person classes last fall. Abroad, implementation of mass testing in Slovakia brought the infection rate down by 60 percent in one week.

Larremore and his colleagues believe cheap, rapid testing would make the current vaccine drive all the more effective. “If we can pile testing on top of vaccines and masks,” he said, “we can drive this pandemic into the ground.”

—Heather L. Frank is a graduate of the WORLD Journalism Institute mid-career course