That immune system training will likely turn future Covid-19 infections into the equivalent of a cold, the authors concluded. Over time, as a degree of protection becomes more standard in adults, the people who will most commonly catch Covid will be young kids, in whom infections even now are rarely serious. That’s the pattern with human coronavirus infections. “I think the scenario … remains the most likely one,” said Marc Lipsitch, an infectious diseases epidemiologist at Harvard’s T.H. Chan School of Public Health. “That essentially, almost everybody has some form of immunity from natural infection and/or vaccination and/or one followed by the other, and that that will persist long enough so that they don’t get really sick when they get it again. And then we transition to endemicity.” Lavine is unfazed by the notion that SARS-2 could still be with us when the pandemic is over. “It’s not a death sentence in any way, shape, or form to say we’re not going to have herd immunity,” she said.