What does that mean for the future of COVID-19? One possible scenario is that the disease could follow the path of the four coronaviruses that cause common colds, which frequently reinfect people but rarely seriously. In one study that tried to infect and then reinfect volunteers with one of these common-cold coronaviruses one year apart, some of the volunteers indeed got reinfected but without symptoms. They also had detectable amounts of the virus in their nose for a shorter period of time. For COVID-19, “the optimistic future is that there are still infections but they are less frequent than now,” Jesse Bloom, a virologist at the Fred Hutchinson Cancer Research Center, wrote in an email, “and most infected people have something more resembling a cold than a life-threatening infection.” (There is speculation, in fact, that the coronavirus OC43 emerged during an 1889 pandemic before fading into the background as a common cold.)

Lavine, at Emory, has co-authored a paper modeling how COVID-19 could eventually end up like these cold coronaviruses. The four that already exist are so common that most of us were probably infected with them in childhood. This early encounter lays down initial immunity against these coronaviruses so that reinfections later in life are milder. Frequent reinfection, when immunity fades and the cold coronavirus evolves, may also update that immunity.