Are immunity certificates the aftermath of COVID-19?

A thought experiment for after the lockdown

„Tickets and IC‘s, please!“, the three public transport employees call friendly but firmly when they enter the car. Everyone lifts their smartphone in anticipation of showing their ticket app but also gets out their wallet — everyone but one young professional in a dress suit. She starts to moan and curse.

“Sorry, ma’am, I need to see your immunity certificate for our day to continue”, the conductor says, while the lady persists to furiously scramble through her bag and pockets…

I was pondering the aftermath of this current COVID-19 situation when I read about people becoming immune to the disease. It’s currently assumed that most people will have some form of protection against becoming infected again. One thing however is unclear: for how long.

If we assume that the duration of immunity is less than five years and that the SARS-CoV-2 virus will stay around for more than that, I would like to know for myself whether and when I am immune. This can be tested based on the antibodies in an individual. In fact, it is likely that such tests will be available soon and will cost only a few dollars.

But knowing myself is only one aspect of this: as many of us are currently experiencing, this virus is a joint responsibility. Not getting infected isn’t life-saving for most people themselves. Not being at risk to infect others, however, is life-saving for them.

Immunity thus seems to be a property that’s relevant to society. Or should I say: feature?

In many communities, a lockdown currently prevents everyone to leave their house, work, or meet. Assuming this cannot continue, can we not let those people roam free who are immune? They cannot spread the virus, can they?

To be sure, they would need to be tested, and regularly. Maybe they would receive an immunity certificate, like in the fictitious excerpt above.

What would this mean for society, though? The obvious continuation of the story is this: the woman cannot find her immunity certificate, which leads to everyone being convoyed out of the car and being isolated and held in a hastily called mobile unit. There, they could crosscheck a central directory for her immunity, or have her immunity checked, or …? Depending on the outcome, everyone would show up to work late. In the worst case, after another 14 days of isolation.

To me, this sounds both probable and like part of a fascist dystopia, based on immunity.

So my questions are these: what assumptions have I gotten wrong? And: what other ways have we to handle the aftermath, as a society and in the story above?