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Coronavirus

Let’s Explore the Promise and Unknowns of COVID-19 Antibody Testing

Because the virus is so new, there are mixed messages about the effectiveness of antibody tests.

Antibody testing for COVID-19 is ramping up nationwide with the hopes that it will help society and the economy return to normal. But without clinical trials and additional time to study the accuracy of the tests and the effectiveness of antibodies, many questions remain about how impactful it will be.

The state of Texas is opening up, and from the looks of things around town last weekend, social distancing, wearing masks, and other precautions to prevent the spread of COVID-19 aren’t being widely observed, even as Dallas County increases its confirmed positive cases. An antibody test, which checks the blood for antibodies that linger after an infected individual has recovered from exposure to the coronavirus, may help better understand how COVID-19 has spread through a community.

“Everybody is anxious to get back to work, but of course the devil is in the details regarding what can we do to maximize protection of the public while we reopen,” says Dr. Larry Schlesinger, who is the CEO and President of Texas Biomedical Research Institute, an independent research institute working exclusively on infectious diseases.

Schlesinger is concerned about a second wave as the state comes back to life too quickly. “We can almost predict accurately that we are going to see some resurgence … as a result of reopening community interfaces. The next one to three months will be very telling as to whether we have been too aggressive or not.”

So how will antibody testing factor in? There have been unapproved antibody tests floating around for weeks, but many of them resulted in false positives and negatives. It wasn’t until last week that the Food and Drug Administration gave emergency use authorization to a blood test for antibodies.

The test looks for markers of immunity in blood that indicate if an individual was affected, and how long ago. But there are different tests, and not all of them are accurate. If you are arranging an antibody test, it is important to be sure it is one of the provisionally approved tests that are performed by an established lab.

Most testing done at hospitals is legitimate, while at-home tests can be more suspect. “It is important for people to understand that not all kits are equivalent,” says Dr. Trish Perl, Chief of Infectious Disease at UT Southwestern. “You have to know who is making the kit.”

While there might be more certainty around affirming antibodies in those who have recovered from COVID-19, finding out what to do with that information is more complicated. 

“The jury is still out on what it means if you have the antibody, says Dr. Jay Woody, chief medical officer of Intuitive Health and a co-founder of Legacy ER & Urgent Care, which have been administering antibody tests since they were given emergency approval by the FDA last week. “The presumption is that you would be able to fight off the exposure and new infection and that those antibodies are a surrogate to fight the disease.”

But only time will tell if that is the case for COVID-19. Whether those antibodies fight off COVID-19 after another exposure, and for how long those antibodies are effective, is still somewhat unknown because the virus is unique and novel. When treating other diseases, antibodies developed through a vaccine or by actually having the disease can last a lifetime or just a few years. Only time spent following and studying recovered COVID-19 patients will deliver those answers.

Perl says there have been animal studies showing short-term immunity with COVID-19 antibodies, but that doesn’t mean the same results will occur in humans. “If you tell me you have received the test and tested positive, I will say you still need to wear a mask and social distance,” Perl says.

There are still doubts around the provisionally approved antibody tests, Schlesinger says, and having false confidence about immunity could make someone take unnecessary risks. “The fundamental problem with antibody tests is our uncertainty as to whether the antibodies being tested prove whether somebody is immune,” he says. “There is a lot more science necessary to understand that. The tests have not passed muster when it comes to clinical utility.”

In addition, not much is known about how herd immunity factors in. In other infectious diseases, a certain percentage of the population has to have been vaccinated or have had the virus for the group to be safe. In measles, it is 95 percent. While that level of immunity won’t be possible without a vaccine for COVID-19, much is still unknown. Perl says that with other coronavirus strains like SARS, antibodies provide immunity for between two and six years, so it may be a while before we have similar data for the latest virus. “We need to not let people get overconfident until we have the appropriate data,” she says.

Woody’s clinics have administered hundreds of antibody tests over the past couple weeks, and he is hoping that the increased data collected by him and other providers can give public health officials a better look at how many people have had the disease. That information will impact and hopefully decrease the hospitalization and death rates, which could be inflated because of a lack of testing.

While antibody testing will help public health officials better understand how the disease spreads throughout the population, the test itself may not be enough to bring things back to normal. Knowing that one coworker has the antibodies doesn’t necessarily mean another one can’t get sick, and a negative test just means the person is more vulnerable or even that they are currently infected, Perl says.

But Schlesinger says that long range epidemiology is what is necessary to know for sure in whether the antibodies will make someone safer.

“In terms of reopening,” he said, “I think it is not a test that is very helpful right now.”

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