Thinking about getting a COVID-19 antibody test? Here’s why medical experts urge caution

COVID-19 antibody tests have been around since the beginning of the pandemic.

Remember talk about immunity “passports” that would verify that you’d been infected and were purportedly immune to COVID? They were supposed to give people freedom to travel risk-free and be around others, in pre-vaccine days.

They never took off. Then the public’s interest in testing for all things COVID waned as the pandemic dragged on. But lately there’s new interest in antibody tests as people try to find out if their vaccine shots are still working or whether they need the shot at all.

The Johnson County Sheriff’s Office put antibody testing back on a local front burner with its plans to spend up to $30,000 on antibody tests for employees to test their immunity to COVID-19. Hundreds in the department have reportedly already signed up.

Sheriff Calvin Hayden has said that people who say the offer is “all about” whether or not to get the vaccine are missing the point.

“This issue is so much more than that. This is about valuing, empowering and supporting individual decisions,” he said in a statement.

But medical experts caution people against making decisions about getting vaccinated based on the results of an antibody test.

A test might reveal you have antibodies, but it can’t tell you if they will keep you from getting infected or very sick. The tests available to the public generally don’t offer the most accurate information of how resistant you are to getting reinfected, researchers say.

The U.S. Food and Drug Administration has reminded the public and health care providers that results from authorized antibody tests “should not be used to evaluate a person’s level of immunity or protection from COVID-19 at any time, and especially after the person received a COVID-19 vaccination.”

Both the FDA and the Centers for Disease Control and Prevention say antibody testing should not be used to decide if someone should be vaccinated.

What are antibodies?

The tests look for antibodies in your blood that can fight the coronavirus that causes COVID-19 — an indication that you’ve been previously infected or vaccinated.

Antibodies are proteins created by your body’s immune system soon after you have been infected or vaccinated that help you fight off infections. Some antibody tests will only detect antibodies from infection and not from being vaccinated.

What a positive result means

A positive antibody test result shows you may have antibodies from a previous infection or from vaccination, the CDC says. It does not mean you have a specific amount of immunity or protection from infection.

You can test positive for antibodies even if you never had COVID symptoms or haven’t been vaccinated — you could have had an asymptomatic infection. Always talk to your health care provider about what the test results mean. They might suggest having a second test for comparison.

Ask your doctor

Talk to your health care provider, or state or local health department, if you have questions about whether to take an antibody test.

The FDA has suggested that antibody tests should only be ordered by health care providers “who are familiar with the use and limitations of the test.” Tests are available through labs, clinics and some pharmacies, and at-home testing kits are available online.

Some doctors worry that people are seeking antibody tests for the wrong reasons.

“Doctors are ordering antibody tests for people who are worried about waning immunity, but I see that as problematic,” Dr. Alan Wells, director of clinical labs at the University of Pittsburgh Medical Center, told Stateline, which reports on trends in state policies.

“For a normal person, knowing your level eight months later (after their initial vaccine dosages) is of relatively little value.”

Stay vigilant

Scientists continue working on trying to understand what a positive or negative antibody test means, “beyond the presence or absence of antibodies,” the FDA says.

For now, the level of protection those antibodies offer is not well understood, the World Health Organization cautions.

If antibody test results are interpreted incorrectly, the FDA warns, people might take fewer precautions against the virus, which could increase their risk of getting infected and spreading it.

That’s why medical experts — especially now that the first case of the new variant, Omicron, has been reported in the United States — still encourage people to follow social distancing guidelines and wear masks and face coverings in public.

And, “all patients regardless of immune status should receive the COVID-19 vaccine,” the CDC says.