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As the world continues to fight against Covid-19 with lockdowns and social distancing, the notion of antibody screening—using data from serology tests to determine who is eligible to participate in society—is gaining traction. Policymakers in Germany, Italy, and the UK, plus some US health experts, have floated the notion of rolling out “immunity passports” that would certify that a person has contracted the virus, recovered, and now has the antibodies required to be immune.

The concept has its issues—but already, there’s an app for that. Bizagi, a UK-based tech company whose normal business is helping companies like Adidas and Occidental Petroleum digitize their operations, today released “CoronaPass,” an app that will use an encrypted database to store information about users’ immune status, based on antibody test results provided by the user’s hospital or other healthcare provider.

Gustavo Gómez, the company’s CEO, said in an interview that he has been in touch with numerous companies and local governments about implementing the app, which would present a QR code that a government or company official could scan to certify that a person’s immunity status has been verified, allowing them to return to work, board an airplane, or otherwise relax their social distancing. He declined to provide more details about where or by whom the app might first come into use.

Related slideshow: COVID-19 outbreak around the world (Provided by Photo Services)

The idea is compelling, in theory. It’s clear that the economy will continue to suffer until immunity to the virus is widespread, and there’s no reason to keep people away from their jobs or families if they are, in fact, immune.

But there are still many holes in scientists’ understanding of immunity to SARS-CoV-2, and it’s far from clear that existing antibody tests can reliably confirm a person’s immune status. Immunity passes like CoronaPass may not be very useful—and may even be counterproductive—until we know more about the body’s immune reaction and how to measure it.

Passport to nowhere

Serology tests detect antibodies produced by an infection, which typically are detectable seven or more days after symptoms of a Covid-19 infection appear. For some pathogens, the immunity conferred by those antibodies could be permanent; for others, it could be nonexistent. Past research on similar coronaviruses suggests antibodies to them may last a year or more—but that their power to neutralize the virus degrades over time. For SARS-CoV-2, the duration of antibodies is unknown, as is their neutralizing power.

Early data from China showed a wide range of antibody responses among 175 infected individuals, including 30% that showed minimal or no “neutralizing” antibodies—a sign that the immune system managed to beat the virus without developing the long-lasting antibodies that confer durable immunity. That result was especially common in young patients. There have also been unconfirmed rumors of reinfection, although the real culprit in those cases may have been testing errors.

But either way, because of all this variability, current antibody tests are not able to say for sure that a person has lasting immunity—even if you’re certain they were infected.

Then there’s the issue of test accuracy. The first serology test to be officially authorized by the FDA purports to be 93.8% accurate for positive results, and 96.0% for negative results. That means that out of 100 people who were given that test, showed antibodies, and received their “CoronaPass,” six could have false results and go back into the world still vulnerable to infection. Conversely, there’s no guarantee that the minimum concentration of antibodies detectable by the test is the same concentration needed to confer immunity.

“When we think about testing for antibodies in blood, we think about a ‘yes’ or ‘no’ answer,” said Jonathan Abraham, an immunobiologist at Harvard Medical School. “But the real question is, ‘Are they going to be enough to protect the individual should they be re-exposed to the virus?’ And that’s just not known yet.”

Answering those questions will take time, Abraham said. And even with perfect knowledge of the SARS-CoV-2 immune response, any pass would also need to consider factors like whether a person has an autoimmune disorder or is taking immune-suppressing medication. Ultimately, he said, it will likely make more sense to express a person’s immune status in terms of a probability, rather than a simple yes/no.

In addition to the few officially authorized tests, the FDA has allowed dozens of companies to market serology tests without authorization, and has already had to crack down on some shoddy ones. So one person might get a rock-solid result from a gold standard test at a research hospital, while another gets a knockoff test at the local urgent care clinic—and both could get the same pass.

“Rolling this kind of approach out now, without clearly defined test characteristics, seems really too soon, even though we want to open the economy,” said Rich Davis, director of the clinical microbiology lab at Providence Sacred Heart hospital in Spokane.

Private vs. public

Gómez, from Bizagi, said that the company is leaving these medical questions in the hands of local government agencies and doctors: They set the criteria for what counts as a valid test, who qualifies as immune, and how long that certification should last. The app also allows individual governments to accept, or not, validations from other jurisdictions.

“‘Safe’ is defined by the doctors,” he said. “Even if it lasted for one month, that would change everything.”

What about privacy? Gómez said the company is HIPAA compliant and won’t hold any patient data other than immune status, which will be kept in an encrypted cloud database accessible only to governments or companies that are able to use the “requesting” side of the app. Patients can delete their profiles any time, and the company recommends that photo ID be used alongside the app to prevent fraud.

In any case, the more relevant law in the US is likely the Americans with Disabilities Act, said Glenn Cohen, a bioethics expert at Harvard Law School. ADA normally prevents employers from asking questions about an employee’s health that could be used to discriminate against them. But in the context of the Covid-19 pandemic, the US Equal Employment Opportunity Commission has loosened some ADA restrictions, including allowing employers to ask employees about relevant symptoms and taking their temperature.

“It pretty clearly signals the direction they are going,” Cohen said, “which is that [requesting antibody test results] will be deemed permissible, but they haven’t quite said that yet.”

Ultimately, the thorniest issue of all may not be immunology or the law, but social inequality. Diagnostic tests are already more readily available for the wealthy. Will the same be true for serology tests and “immunity passports,” with certain people shut out of society while others are allowed back in? Stanford University historian Kathryn Olivarius tackled that question in a New York Times column, and surfaced some disconcerting answers from the records of yellow fever outbreaks in the 19th-century Deep South.

“The most vulnerable people in our society cannot be punished twice over,” she writes. “First by their circumstance and then by the disease.”