As vaccination drives roll out at varying speeds, there's a big question mark over the issue of what may become—hopefully temporarily—a two-tiered populace.

In Israel, which is running the world's speediest COVID-19 inoculation campaign (though that hasn't warded off the need for a tight new lockdown), the health ministry has unveiled a "green passport" that will allow vaccinated people to do things like attend mass gatherings and sporting events. It said the passports will also probably be used by hotels, malls and restaurants.

On the other side of the world, in Los Angeles County, vaccine recipients are getting a digital record, stored on their smartphones, that could end up being used for entrance to concerts or flights.

Some airlines are quite keen on the idea, as a way to return to quasi-normality. Qantas said a month ago that it would require passengers to be vaccinated first if they are to get on-board this year—a step beyond the industry-wide push for a standardized way to show that passengers have at least been tested before departure.

The debate over preferential treatment for vaccinated people is one that's loaded with many, many factors ranging from the behavioral to the ethical. Would the promise of benefits push skeptics to become vaccinated, or would their withholding be seen as evidence of the vaccination drive being some kind of authoritarian conspiracy? What about people who can't get vaccinated, for reasons ranging from their personal medical circumstances, to the failure of governments to inoculate people quickly enough?

For officials, these quandaries veer into the territory of human rights—always a balancing act, so they will have to tread carefully due to the constitutional implications.

But what about businesses? Many will undoubtedly have to comb through legal implications too, but, especially in the absence of official rules on the subject, their big issue will be deciding whether or not to continue treating all their customers equally.

For example, once a sizeable proportion of the local populace has been inoculated against COVID-19, will retail chains face pressure to let vaccinated people into their outlets without a mask? Will vaccine resisters then complain that they're being discriminated against? None of the currently-available vaccines are authorized for use in kids—does that mean cinema operators might have to discriminate against young moviegoers?

In a sense, it's great to be able to ask these questions—let's never forget how incredible it is that vaccines are already being rolled out, barely a year into the pandemic. But I certainly don't know what the answers are, and I'm fascinated to see how they materialize.