Lack of certain antibodies would mean you don't have an "immunity passport" and are therefore not allowed to venture out in public. Those who have them would be issued certificates to roam and restart economies -- so the vulnerable can stay home.
But the World Health Organization and other experts say that's a terrible idea.
"So many flaws that it is hard to know where to begin," molecular biologist Natalie Kofler, founder of the global initiative Editing Nature, and Canadian bioethicist Françoise Baylis, said in a commentary published in Nature.
They listed reasons why they think it's unworkable and unfair:
So many unknowns: For starters, they wrote, it's not clear whether people develop any kind of lasting immunity after a coronavirus infection. The World Health Organization has warned governments against issuing immunity passports, saying there's no evidence people who have recovered from Covid-19 are protected from a second coronavirus infection.
The tests can't be trusted: Then there's the fact that while antibody tests are crucial in determining past exposure to coronavirus, not all available antibody tests are reliable. Some antibody tests had high rates of false positives in screenings performed by a consortium of California laboratories. A false positive means someone would be told they'd been previously exposed to coronavirus when they had not.
Nor are they available for everyone: There aren't enough tests for everyone who needs them. In the US, more than 1.5 million people have tested positive for coronavirus. The current calculation is almost certainly an undercount, said Dr. Peter Hotez, professor at Baylor College of Medicine.
There are not enough survivors: If only coronavirus survivors are allowed to contribute to the economy, there won't be enough manpower to keep it humming. "Low disease prevalence combined with limited testing capacity, not to mention highly unreliable tests, means that only a small fraction of any population would be certified as free to work," they wrote.
Privacy's a concern: There's also the issue of privacy. Ethically, they argued, monitoring erodes privacy.
So is marginalization: Monitoring people to see who's immune would affect already marginalized groups. We've already seen this during this pandemic when more blacks and Hispanics were arrested for violating physical distancing laws in New York. "With increased monitoring comes increased policing, and with it higher risks of profiling and potential harms to racial, sexual, religious or other minority groups," they wrote.
And labeling, too: It'll create even more divisions. "Labeling people on the basis of their Covid-19 status would create a new measure by which to divide the 'haves' and the 'have-nots," they added.
More discrimination: New forms of discrimination could emerge as any program for certifying immunity could be expanded to include other forms of personal health data. "The immunity passports of today could become the all-encompassing biological passports of tomorrow," they wrote.
Willful infections: Finally, immunity passports could encourage people to get infected on purpose. "If access to certain social and economic liberties is given only to people who have recovered from Covid-19, then immunity passports could incentivize healthy, non-immune individuals to willfully seek out infection — putting themselves and others at risk," they wrote.
Better approaches include old-fashioned identification and tracing of infected people and their contacts and development of a vaccine, Kofler and Baylis argued.
CNN's Vasco Cotovio, Sarah Dean, Susanne Gargiulo, David Culver and Nectar Gan contributed to this report.