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COVID-19 Antibody Testing: Questions Remain

photo of coronavirus cell

April 27, 2020 -- Jenny Cook was diagnosed with COVID-19 in March. Now, the 26-year-old MBA student at Duke University is trying to put her illness to good use.

Cook, a Champaign, IL, native, enrolled in Duke’s research into a COVID-19 antibody test.

“I think it is important to participate in clinical research studies so that I can help researchers understand and fight COVID-19,” she told WebMD. “I have been lucky enough to not have any symptoms from this disease, but not everyone has been as fortunate.”

COVID-19 is the disease caused by the coronavirus that sparked a global pandemic. There are more than 950,000 reported cases in the United States.

As scientists and researchers race to find diagnostic tests, vaccines, and treatments for this new virus, antibody tests, also called serological tests, are being researched and scrutinized.

The tests detect antibodies -- the body’s immune response to infection -- in the blood. If there are antibodies, that means the person has been exposed to the virus and may have some level of protection against reinfection.

New Concerns over Tests

But that theory was rocked late last week when a new World Health Organization guidance declared there is no proof that the presence of antibodies means a patient cannot be infected again.

“Laboratory tests that detect antibodies to [the coronavirus] in people, including rapid immunodiagnostic tests, need further validation to determine their accuracy and reliability,” the WHO says in the new guidance.

Part of the problem, the agency says, is that the antibodies found in patients’ blood may be from this new coronavirus, officially known as SARS-CoV-2. But the antibodies could also be from any of the six other known coronaviruses, including several that cause the common cold.

“People infected by any one of these viruses may produce antibodies that cross-react with antibodies produced in response to infection with SARS-CoV-2,” the WHO says.

Still, scientists around the world continue to explore antibodies as a possible sign of immunity.

Progress Made in Analysis

On Thursday, New York Gov. Andrew Cuomo announced early results of his state’s first randomized antibody testing. Of the 3,000 New Yorkers tested, about 14% were infected and developed antibodies.

In Los Angeles, some 800 county residents have visited drive-thru testing sites. According to Georges Benjamin, MD, executive director of the American Public Health Association, a little over 4% of adults in the county were antibody-positive.

At Duke, Thomas Denny is a professor of medicine and chief operating officer at the Duke Human Vaccine Institute. The test they’re using is part of a research study to find out if a positive antibody test means future protection.

"The antibody test will help us understand a term that we call ‘penetrance,’ and what that means is how much of that disease, in this case COVID, has been in the local community that you’re looking for,” he says. “That will help us understand as we get ready for what may be a second round of problems, COVID infections coming in the fall. By that point, we should know if you have antibodies, does it equate to offering protection.”

Denny doesn’t want to see antibody testing give people a false sense of security about their level of immunity and feel they can relax on things like social distancing. He urges caution until the data is clear.

“We hope that one would develop an antibody response that would confirm protection as we’ve seen with other infectious diseases, but until we have the data that proves that we don’t know for certain, and I think we need to be a bit cautious in where we’re going with all of it until we have the data that confirms it,” he says.

FDA Commissioner Stephen Hahn said in a statement that there is still so much we don’t understand about COVID-19 immunity.

“For example, we don’t yet know that just because someone has developed antibodies, that they are fully protected from reinfection, or how long any immunity lasts,” he said.

Still, he said, widespread antibody testing “will help us track the spread of the virus nationwide and assess the impact of our public health efforts now, while also informing our COVID-19 response as we continue to move forward.”

The FDA has reviewed and given the OK for four antibody tests to be used under the agency’s emergency use authorization process.

Data Has Great Value

Antibody testing has the potential to help determine when Americans can return to work and resume normal activities, as well as who can donate blood that can be used to make convalescent plasma to help those who are gravely ill.

In his statement, Hahn said the FDA is allowing developers to request approval for tests through its emergency use authorization process, and is working with the National Institutes of Health and the CDC to evaluate these tests.

But, Hahn said, they won’t object if developers market or use their tests without prior FDA review as long as they follow three rules: The developer validates it has determined the tests are accurate and reliable, the developer notifies the FDA of its own validation, and the tests are labeled appropriately, including that they are not to be used as a sole basis for diagnosis.

Still, not everyone is playing by the rules.

“Some test developers have misused the serology (antibody) test kit notification list to falsely claim their serological tests are FDA-approved or authorized,” Hahn warned. “Others have falsely claimed that their tests can diagnose COVID-19.”

Diane Griffin, MD, a professor at Johns Hopkins Bloomberg School of Public Health, is concerned about the quality of some of these tests.

“It’s always a worry that there’s going to be a problem, but I don’t have any personal knowledge that there are problems with any particular test. Those usually emerge as people start using them widely.”

Griffin says all these tests look at sensitivity and accuracy to detect antibodies, but almost none are 100% in both categories.

So will they give people a false sense of security?

Not a ‘Magic Bullet’

“I guess the concern is that these people will now quit their social distancing and not stay at home, but that is what people are hoping to accomplish by doing antibody testing: Identify people that at least could go to work, identify people who are at less risk of contracting the infection in the community.”

Maureen Long, PhD, is an expert on viruses and emerging diseases at the University of Florida’s Emerging Pathogens Institute.

“I’m really concerned that the antibody test results will be used to recommend to individual people to either go back to work or to resume somewhat normal activities based on their antibody responses in their blood,” she says. “As we move forward, testing actively infected people and performing contact tracing becomes even more essential.”

Long says antibody testing for the new coronavirus is much more nuanced than people understand.

“Everybody wants a magic bullet for testing, and I’m not so sure we can provide it because everything’s happened so rapidly,” she says. “I’m not saying it isn’t useful, it isn’t important to develop these tests and to take them forward; I’m really concerned, though, what people will use them for.”

For Jenny Cook, the Duke MBA student, taking part in antibody research is purely altruistic.

“I have elderly grandparents, and if they were infected, I would want to know that I did everything I could to help,” she says. “Maybe my blood could lead to a cure. I am not a doctor or a nurse, so this is just my way of trying to do my part.”

WebMD Health News Reviewed by Neha Pathak, MD on April 27, 2020

Sources

World Health Organization: “‘Immunity passports’ in the context of COVID-19.”

Jenny Cook, Durham, NC.

Thomas Denny, professor of medicine, chief operating officer, Duke Human Vaccine Institute, Durham, NC.

Stephen M. Hahn, MD, commissioner, FDA.

Diane Griffin, MD, professor of molecular microbiology and immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore.

Maureen Long, DVM, PhD, Emerging Pathogens Institute, University of Florida.

FDA.gov: “Coronavirus (COVID-19) Update: Serological Test Validation and Education Efforts,” “Emergency Use Authorizations.”

CDC.gov: “Cases of Coronavirus Disease (COVID-19) in the U.S.”

COVID-19 Dashboard by the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University (JHU)

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