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Can Home COVID-19 Tests Catch BA.5?

Many of us have come to rely on rapid tests for catching COVID-19 and peace of mind. Here's how they fare against omicron.

A hand holding an at-home COVID-19 test strip against a bright red background
Sarah Tew/CNET
For the most up-to-date news and information about the coronavirus pandemic, visit the WHO and CDC websites.

BA.5 is causing most cases of COVID-19 right now. The newest subvariant of omicron is extremely contagious and it's resulting in more reinfections in people who've already been sick with COVID-19, including during earlier omicron waves.

But are the at-home rapid tests we've come to rely on (and have even gotten shipped to our homes) able to detect BA.5? 

Right now, current science tells us that the home tests shouldn't be any worse at detecting BA.5 than they are at detecting other versions of omicron. But the US Food and Drug Administration changed its guidance slightly this month in an effort to reduce the likelihood of a false negative result (possibly confusing the public in the process). The FDA now says that people who were exposed to COVID-19 but have no symptoms should test three times, each test 48 hours apart, instead of the two times recommended by many home test manufacturers. This is in line with research that shows repeat testing over a wider range of time has a better chance of detecting COVID-19. 

Here's what to know about BA.5 and home tests.

How do home COVID tests work? 

At-home COVID-19 tests are usually rapid antigen tests, which work by identifying proteins in the coronavirus. If the proteins are present in your nose when you swab it, there will be a second line on your test, and you should consider yourself positive and contagious with COVID-19. 

"Positive results remain highly accurate for these tests, though there still can be false negatives," Shaili Gandhi, vice president of pharmacy at SingleCare, said in an email. This is because it takes a higher amount of virus to test positive on a rapid test than the highly sensitive PCR or lab-based tests. Someone who's fully vaccinated and boosted, for example, may have a very low viral load (smaller amount of virus) and that may mean they test negative even if they do have COVID-19. If that's the case, you might need a lab-based PCR test before COVID-19 is confirmed. (That doesn't mean you shouldn't use a home test if you're boosted, though, but more on that below.)

A young woman dips a nasal swab into a tube for a COVID test

Many of us are familiar with the swab, dip, swirl and drip method of testing for COVID-19.

Tang Ming Tung/Getty Images

Can home tests detect BA.5? When's the best time to test? 

Research continues on BA.5, which includes how effective tests are at detecting it, according to Gandhi. But how well the home COVID-19 tests work may have less to do with the subvariant and more to do with when you test. 

You're most likely to test positive for COVID-19 when you have symptoms. Similarly, asymptomatic people or someone with mild symptoms might be more likely to have a false negative result than someone who has a lot of symptoms. 

"Under these conditions, at-home tests are as effective at detecting omicron as with other variants," Sandra Adams, a professor of biology and virologist at Montclair State University, told New Jersey Advance Media

"The accuracy varies with when the tests are taken," she added.

Gandhi said a "good rule of thumb" is to take at least two tests, with a day or two between tests. You should also follow the instructions on the box, which often comes as a pack of two tests, and stay up-to-date on the US Food and Drug Administration's extension of the shelf lives of some home tests. The FDA also now recommends a third test for people who were exposed to COVID-19 but don't have symptoms. It recommends repeat testing after a negative test regardless of your symptoms. 

And, if there are home tests discovered to not work against BA.5, the FDA will remove its authorization of that particular test. 

"The FDA would know if there are performance concerns because they continue to monitor all authorized tests and scientific evidence over a period of time in the event that they need to make changes," Dr. Mark Fischer, Regional Medical Director at International SOS, said in an email.

What's BA.5's incubation period? 

At the beginning of the omicron surge in December last year, the US Centers for Disease Control and Prevention changed its quarantine guidance based on the understanding people were most contagious with COVID-19 in the one or two days before they developed symptoms, and two to three days after. 

While some research suggests BA.5 doesn't have a different incubation period than other versions of COVID-19, some people are reporting testing positive for longer, Gandhi notes. Dr. Eric Topol, a professor of molecular medicine at Scripps Research, noted in a report earlier this month that changes in BA.5 that make it easier to get into cells may explain why some people are taking a long time to test negative. 

"For now, while this new variant is still elusive, I recommend testing multiple times with at-home tests, and if symptoms persist [and you're still testing negative], get a PCR test from your pharmacy or doctor," Gandhi said. 

Unfortunately, a positive result on a home rapid test in all likelihood means you have COVID-19. So consider yourself contagious and follow the CDC's guidelines for isolation and masking.

Correction, July 26: The spelling of Shaili Gandhi's last name has been fixed.

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.