This, then, could count as a sort of consolation prize for the many vaccinated people who have recently been hit by a version of the virus. Post-vaccination infections might, in theory, influence immunity in ways our vaccines can’t. While nearly all of the world’s COVID vaccines center on SARS-CoV-2’s spike protein, fighting the actual virus gives the body more information about its anatomy. Bona fide microbes can also draw airway-specific defenses to the nose and mouth, the virus’s natural point of entry—something in-the-arm injections aren’t great at doing. “If those are maintained, that’s what’s going to offer a lot of protection against subsequent infections,” Jennifer Gommerman, an immunologist at the University of Toronto, told me. (Gommerman also thinks that vaccines spritzed up the nose might be a good move in the future.) And since our current vaccines are still based on an old, ancestral version of SARS-CoV-2, a post-vax collision with the highly mutated Omicron offers intel that’s more up-to-date. By rousing immune cells that haven’t responded to previous variants, an Omicron infection could effectively “broaden your immune response,” Rishi Goel, an immunologist at the University of Pennsylvania, told me.

The problem, though, is that none of this is assured, especially when factoring in the thorny variable of time. Viruses that linger too long in the body could exact a punishing cost—transmission, disease, death. But if they’re cleared out too fast, they might not have enough time to teach the body something new. And those dynamics depend partly on when someone got their last immunological boost. Someone who’s very recently received a vaccine, for instance, might still be flush with antibodies that could swiftly sweep out the virus. Ellebedy, who was exposed to his COVID-sickened wife about a month after boosting and had pretty minor symptoms, thinks that’s what happened to him, which is great from a disease-severity standpoint, and potentially a transmission one. But a truncated infection might also cut short the immune system’s review session on the virus itself. Bodies will sometimes try to calibrate their defense to match the opponent’s offense, and trifling infections aren’t always worth a massive reinvestment in protection. A later encounter with the virus might spur cells to react more dramatically and squirrel away another slew of safeguards—but at the risk of a longer, more dangerous, and more contagious infection.