Are at-home COVID tests still effective? Here's what you should know – San Francisco Chronicle

The federal government plans to distribute more free home test kits to Americans amid the winter COVID surge. But with new variants of the coronavirus in circulation, are at-home tests still effective?
As Americans experience their third holiday season of the pandemic, millions are gathering and traveling to see family and friends. The White House on Thursday announced a limited distribution of free at-home test kits to curb the spread of COVID-19 during the holidays. But the news came only a few days after the U.S. Food and Drug Administration had warned that some COVID rapid antigen tests may be less reliable in detecting omicron subvariants such as BQ.1 and BQ.1.1.
Three years into the coronavirus crisis, prevention measures such as mandatory masking and social distancing have largely been eliminated. Most people are vaccinated, and many are boosted and have stocks of home test kits. But in light of the recent FDA caution, are at-home tests still worth using? And what should you do if you need laboratory testing or medication in the San Francisco Bay Area? Here’s what experts say.
Public health experts say they are. It’s not that the tests no longer detect omicron and its subvariants but rather that they may be less sensitive in some cases, said Nadia Roan, an immunologist at UCSF. What that means, she said, is that for some tests, you may need more of the virus to be present in your nose or throat for the kit to register a positive reading. Which tests are less sensitive depends on which parts of the omicron virus they were designed to recognize.
Over-the-counter rapid antigen tests rely on antibodies that latch onto specific parts of omicron surface proteins. The pairing eventually results in the color change users see as a line in the results pane.
“Different companies’ kits use different antibodies. Omicron has a lot of mutations, and some of those mutations may make the antibodies latch on less well, so it becomes harder to get a signal when there’s low levels of virus,” Roan explained. However, the antibodies do not completely lose the ability to detect the omicron subvariants, so the tests still work, depending on how much of the virus is present.
If you suspect an exposure, experts recommend taking a home test multiple times on different days. Testing several times increases the chance of hitting the peak of viral replication, when the most virus is present, Roan said.
Roan recommended swabbing only the nose, “which is what the tests were designed for,” she said. But some doctors also recommend sticking the swab into the back of the throat. Multiple iterations decreases the chance of a false negative — which can provide a deceptive sense of security and lead to inadvertent virus transmission.
The San Francisco Public Health Department also encourages the use of at-home kits. “It is always possible to have a negative test result,” said a spokesperson. “People who have symptoms of COVID-19 but receive a negative result from their at-home test should test again 24 to 48 hours later and take precautions if they are around vulnerable people or higher risk settings.”
It’s the holiday season and historically, COVID infection rates have spiked during this time of the year. Whether and how often you test depends on your own situation.
Generally speaking, there’s no need to take routine COVID tests if you are feeling normal or if you’re clearly suffering from a different winter illness such as a common cold or the flu. (Here’s a guide on how to tell them apart.)
But even if you’re asymptomatic, some experts recommend taking a home test if you are attending a holiday gathering or social event where immunocompromised people or other at-risk individuals will be present, just in case you’ve been exposed and don’t know it yet. In such instances, Roan said, it’s best to test on the day of the party, as well as a day or two before and after.
Of course, if you are experiencing COVID symptoms, take a test immediately at home and if it’s negative, do it again in subsequent days. People who feel sick, regardless of test results, are advised to stay home to prevent the spread of respiratory viruses.
California’s top public health official, Dr. Tomas Aragón, said on Tuesday that anyone who tests positive for COVID-19 should seek immediate treatment, especially at a time when two other respiratory viruses — influenza and respiratory syncytial virus — are filling hospital beds. “Treatments are underutilized, especially by communities hardest hit by COVID-19,” Aragón said in a statement. “They can help keep COVID-19 patients from hospitalization and death.”
Currently available anti-viral medications such as Paxlovid or molnupiravir must be taken within five days of when symptoms start, but are generally available only to older people or those with other risk factors. A large study published Wednesday in the Annals of Internal Medicine found that using Paxlovid was associated with a 44% reduction of the risk of COVID-19 hospitalization or death among highly vaccinated Americans aged 50 and older.
Other longstanding recommendations also continue to apply: Minimize contact with other people, isolate, and wear a mask.
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Even if you feel fine, a positive COVID test means you are likely contagious. (False positives are much rarer on home test kits than false negatives.) You should ask your doctor or health care provider about taking anti-virals such as Paxlovid or molnupiravir, which you can get through pharmacies or community health clinics if you qualify. You should isolate at home until you no longer test positive, which can take up to 10 days or longer.
Health experts say the rapid antigen tests rarely give false positives, but if you get a negative result, it doesn’t mean you’re in the clear. So if you need more accuracy, you can get a lab (PCR) test when you have to know whether you’ve been infected by someone else. “A negative rapid antigen test can be followed up by a lab test just to be more certain,” UCSF’s Roan said.
If you have known exposure and start getting symptoms, it’s not necessary to take a PCR test if the home test is positive, unless you need official documentation of having contracted COVID for work, for example. And some health care providers discourage patients with positive home test results from confirming the results via lab tests, since doing so uses up vital testing capacity and puts health care workers and other patients at risk.
PCR tests are also routinely administered before elective surgery or other hospital admissions.
It depends. If you have health insurance, costs for tests and treatments are likely to be covered or reimbursed. If you don’t have insurance, you can go to state or county-run sites that provide testing and medications for free. Most of these locations require an appointment first.
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Many pharmacies, such as CVS and Walgreens, offer vaccination, testing and antiviral prescriptions. Payment is dependent on insurance carriers, and out-of-pocket testing can cost upwards of $100.
1. In San Francisco, you can get COVID testing without an appointment at these locations.
2. In Alameda, you can go to these sites for free testing though some places require appointments.
3. In San Mateo County, you can go to county-sponsored locations such as Mater Dolorosa Church, the College of San Mateo, and these other places.
4. If you have insurance, contact your doctor to schedule a test. Some hospitals such as Kaiser Permanente still have drive-through testing in a few locations by appointment only, as do other health clinics.
5. Visit a Test-to-Treat location. This tool lets you search by ZIP code on clinics that are providing testing and medications near you.
6. If you don’t have insurance or can’t get medical care within 24 hours, visit or call 833-686-5051 to make a free phone or video appointment. You can only make appointment if you have a positive COVID test result, and are showing symptoms.
7. Call the state COVID-19 hotline at 833-422-4255.
Shwanika Narayan is a staff writer at the San Francisco Chronicle. Email: Twitter: @shwanika
Shwanika Narayan covers Bay Area economic trends, culture and communities at The San Francisco Chronicle. She previously covered retail, small business, e-commerce and trade on the business desk. Before joining the paper in 2019, she worked at The Los Angeles Business Journal and freelanced for AJ+, NBC News, Quartz and Hyphen magazine, covering business news, and general national and global news. Shwanika has a master’s degree in journalism from Columbia University and a bachelor’s degree in political science from UCLA.