The measles virus is ultra-infectious, much more so than SARS-CoV-2, and kills many of the uninoculated children it afflicts. But for those who have gotten all their shots, it’s a less formidable foe, which we’ve learned to live with long-term. That’s the direction that many experts hope we’re headed in with SARS-CoV-2 as it becomes endemic, as my colleague Sarah Zhang has written.

We’re not yet at the point where we can officially label post-vaccination COVID-19 cases as “modified”; maybe we never will be. Some immunized people are still getting dangerously sick. But the shots are softening COVID-19’s sharp edges: On average, breakthrough infections seem to be briefer, milder, and less contagious. Among the fully immunized, catching the coronavirus doesn’t mean the same thing it did last year. “It’s a very different kind of infection than in people who are immunologically naive,” Lindsey Baden, an infectious-disease physician and COVID-19 vaccine researcher at Brigham and Women’s Hospital in Boston, told me.

If this virus becomes as inescapable as the culprits behind the colds and flus that trouble us most years, we could all have to grapple with one of these infections, and learn that lesson on a personal level. That’s the social tax of a forever virus: Nearly everyone may eventually know what it is to get COVID-19—but a tamer, more domesticated version of its pre-inoculation self.