As governments look to lift restrictive measures put in place for the coronavirus, one genre of proposals is to give people who have recovered from COVID-19 a digital immunity pass, passport or certificate. It goes by many names, but the idea is the same. It would say you’re immune and no longer spreading the virus, letting people get back to work, enter shops and engage in the physical world again ahead of the rest of the population.

It makes sense. The world can’t continue to deal with the social and economic costs of this magnitude for an extended period of time. People want to get back to their lives. But doing so in a normal way right now isn’t possible. Immunity certificates, based on more widespread testing, would crack the door to a pseudo-normal world ajar, something that appeals to lawmakers. 

“Everyone staying home is just a very blunt measure. That’s what you say when you’ve got really nothing else,” Emily Gurley, a scientist at the Johns Hopkins Bloomberg School of Public Health, told NPR regarding immunity tests. “Being able to test folks is really the linchpin in getting beyond what we’re doing now.”

Scientists are studying whether people who recover from the virus possess antibodies that may confer immunity for a period of time. The idea is a person would get tested, receive the results of the test and, if they were found to have antibodies, they would be issued a QR code or other digital pass/document that could be scanned or reviewed on their smartphone. That pass would have been issued by a health agency, be timestamped and authenticated as accurate.

Several countries are implementing or close to implementing immunity passes now. Chile's passes, for example, exempt those who have recovered from COVID-19 or tested positive for the presence of antibodies, from quarantining and lets them return to work, The Washington Post reported. Residents of Chile can apply for these passes if they haven’t shown symptoms for the disease and they’re willing to be tested.

See also: Privacy Advocates Are Sounding Alarms Over Coronavirus Surveillance

Germany and the United Kingdom are in the process of pursuing widespread antibody testing, and states in the U.S. are considering similar measures, which is a precursor to issuing passes. China enforced a more draconian form of health pass, which greatly curtailed movement for citizens based on whether their pass was colored green, yellow or red. The color was based on location tracking, travel history and health information, and has been criticized for the lack of transparency as to why certain people are branded with a certain color. 

Immunity passes are likely to be based solely on testing, rather than the various factors that influence China’s system. 

First, there’s a lack of testing being done, which is the basis for any tracing or passport system. The U.S. is  struggling with testing even as thousands of tests sit unused in labs. The Food and Drug Administration has relaxed accuracy standards regarding tests as it rushes to get them to the public, but there are concerns regarding the prevalence of false negatives. False negatives are people who exhibit symptoms of COVID-19 but test negative for the virus, sometimes incorrectly. Just recently, a panel of more than 45 scientists, health experts and economists estimated the U.S. would need to administer 20 million tests every day by mid-summer to open the economy in a safe way. 

“In a situation where the prevalence of people with antibodies in the population is quite low – probably no more than around 10 percent of people – even if you’ve got a highly, highly specific test, it is still going to give you quite a lot of false positives,” Robert West, a health psychologist at the University College London told Wired. “That means the government cannot say to people, 'Because you’ve got this test result, you’ve got the antibodies.'”

Then there’s the question of how long immunity might last. Scientists can’t tell us for certain. Still, immunity passports may be the best-worst option for getting us back to work. 

Maybe. There are still pressing questions regarding how people’s medical data will be protected when it comes to issuing a digital immunity pass, how they will be verified and whether creating essentially two classes of people, one of which would have more freedoms and would disproportionality impact vulnerable populations. 

Countries continue to grapple with implementing contact tracing yet are still considering reopening in the near future. These passes will play a key role in letting people go back to work and businesses to open again, even as debates continue about how they're executed and their unintended consequences.

See also: European Contact Tracing Consortium Faces Wave of Defections Over Privacy

For example, there could be black markets that arise for spoofed certificates, or false ones, that let people who desperately need to go back to work do so. Another concern is whether a record of all people who have passes is kept in a centralized database that could be co-opted for surveillance or hacked for their personal information. Similarly, clear timelines for data storage relating to these passes would need to be clear, lest they continue to exist indefinitely.

For now, in the U.S. at least, these passes may not be mandatory. But, in effect, they could become compulsory. If a private business said people without such a digital certificate couldn’t enter, and such practices became widespread, a pass would essentially become mandatory in practice if not name. There are also concerns about access to digital passes. While 81 percent of Americans have a smartphone, that leaves millions of people who don’t have one. People without phones might have to procure paper passes, which also would have to be made secure. 

These are questions that will need to be answered in the coming weeks and months as the world continues to move through the trajectory of this pandemic.