If you never had any symptoms, it might come as the shock of a lifetime: a positive coronavirus antibody test. But with your positive results in tow, now you can party with loved ones with no fear of catching or spreading COVID-19, right? Wrong, experts say. There are still a lot of unknowns about coronavirus antibodies, but scientists do know they don't actually grant you unconditional immunity from the virus, and testing isn't as reliable as you might think.
What A Positive Coronavirus Antibody Test Means
If you've caught the coronavirus, your body will produce antibodies to fight the virus off. The antibody test looks at your blood to check if these substances are present. If it's positive, it means that you've had the coronavirus in the past, even if you never felt symptoms.
You may have had a test for coronavirus itself (the nasal swab) at the same time as your antibody test (the blood test). If the coronavirus test comes back positive, you need to adhere to all the CDC guidelines for people who are sick. Tell anyone you've recently hung out with about your status, and participate in any contact tracing efforts. You also need to self-isolate for at least 10 days, until your fever has been gone for three days and your respiratory symptoms have substantially improved. You can get another coronavirus test after your symptoms ebb, to ensure you no longer have the active virus in your system. No symptoms? Apply for another test after 10 days, to ensure the virus has come and gone.
It takes at least 12 days after exposure to coronavirus for antibodies to start appearing in your blood, so if your coronavirus test comes back negative and your antibody test is positive, the virus itself has likely gone. The antibodies are the footprint it's left behind.
Can You Stop Social Distancing If You Have Coronavirus Antibodies?
The simple answer is no. For one, antibodies may not stick around that long. New research published by King's College London, which hasn't yet been peer reviewed, suggests that coronavirus antibody levels peak in people with COVID-19 around three weeks after they've first been infected, but decline two to three months afterwards. The sicker people are with coronavirus, the more antibodies they produce. That means that if you were asymptomatic or had mild symptoms, your antibodies could disappear even faster.
"One of the things we're seeing more and more is that some people become infected with coronavirus but never develop an antibody response," Gwen Murphy, Ph.D., an epidemiologist at testing company LetsGetChecked, tells Bustle. "These people must be able to fight off coronavirus infection with other blood cells."
It's also not known whether antibodies for coronavirus can offer much protection from a second bout of the virus, even when they're present in high numbers. In the early days of the pandemic, the World Health Organization thought society could reopen with "antibody passports," or proof that a person had caught and overcome the virus. But research is now showing that's not how the virus works. An article published in Nature examined 89 different antibodies produced by COVID-19, and found that there are some that may provide protection and neutralize the virus — but not all people produce them in high numbers, or at all. If you've been hospitalized or seriously ill with coronavirus, you'll likely be more protected from it in the future, the article says, but there's no guarantee.
Even with a positive antibody test, you still can't attend a big indoor party, go out in public without a mask, or make out with a stranger risk-free.
What To Do After A Positive Antibody Test
Some experts suggest you should try to get a second test, as false positives are a strong possibility. "Many of these tests are not FDA-approved," Dr. Larry Burchett M.D., an emergency physician, tells Bustle. Information about FDA status should be on the test itself, or on the results, but if you're not sure, you should enquire with the laboratory that tested your sample. Not FDA-approved? See if you can get another with FDA certification.
But "even with the better, FDA-approved tests, there will be false positives," Dr. Burchett says. A review of 54 studies of antibody tests published in Cochrane found that antibody tests may be less reliable in people who've had coronavirus five or more weeks ago, and in people who have milder symptoms. There also hasn't been much research on antibody testing in people who weren't hospitalized for coronavirus. If there are antibody test shortages in your area, it's worth discussing a second test with your doctor to see if it's a good idea.
Experts recommend that you shouldn't change your behavior just because you've tested positive. The results indicate that you had coronavirus at some point, which is something that should be shared with your doctor, but it doesn't mean you can't catch it again. "If you receive a positive result on a coronavirus antibody test it means that you probably recently had COVID-19," Murphy says. "Unfortunately, you might still get sick again, so you should certainly stay home if you are sick, practice social distancing, wash your hands frequently, and wear a mask in public." If you get any symptoms or are around somebody who's been exposed to coronavirus, get tested for the virus as usual. Any information about this virus can help researchers understand it better.
One thing you can do for COVID-19 research is donate antibody-rich plasma. The FDA is asking anybody who's fully recovered from the coronavirus, with no symptoms for 14 days, to donate their plasma, which is being used as a coronavirus treatment.
Coronavirus antibodies aren't vaccines, and we're a long way from anything that can promise you'll never get the illness again. "You should continue taking preventative measures to protect yourself against infection," Dr. Seema Sarin M.D., an internal medicine physician with healthcare provider EHE Health, tells Bustle. At least you can keep wearing that cute mask you made.
Dr. Larry Burchett M.D.
Gwen Murphy, Ph.D., MPH
Dr. Seema Sarin M.D.
Deeks, J.J., Dinnes, J., Takwoingi, Y., Davenport, C., et al. (2020) Antibody tests for identification of current and past infection with SARS‐CoV‐2. Cochrane Database of Systematic Reviews. 6. Art. No.: CD013652. DOI: 10.1002/14651858.CD013652.
Robbiani, D.F., Gaebler, C., Muecksch, F. et al. Convergent antibody responses to SARS-CoV-2 in convalescent individuals. Nature (2020). https://doi.org/10.1038/s41586-020-2456-9
Seow, J., Graham, C., Merrick, B., Acors, S. et al. (2020). Longitudinal evaluation and decline of antibody responses in SARS-CoV-2 infection. medRxiv. 10.1101/2020.07.09.20148429