COVID-19 is not the flu, and no one knows for sure exactly how often we’ll have to immunize ourselves against it. But it seems inevitable that someday, the entire American public will be asked to sign up for shots again—perhaps quite soon, perhaps every fall, as some vaccine makers would like. We have just one template for this: the flu shot. And expecting even similar levels of so-so uptake may be optimistic. “I’m guessing that flu-vaccine coverage is going to be a ceiling,” says Alison Buttenheim, a behavioral scientist at the University of Pennsylvania. “I just don’t think we’ll have 70 percent of U.S. adults saying, Oh, an annual COVID shot? Sure.”

Immunization ennui is already playing out. Months into the COVID-booster-shot rollout, only half of Americans eligible for an additional injection have gotten one—that’s with the pandemic still raging, with more than 1,000 people dying each day in the United States alone. “We’re already losing the immediate motivator of, I’m afraid I’ll get sick and die,” says George Dehner, a flu historian at Wichita State University.

If the future of COVID shots ends up mirroring the past and present of flu vaccines, we’ll have our work cut out for us. But many of the barriers we face now in trying to get people to sign up for their shots, not just once, not just twice, but likely many times over, don’t have to feel like uncharted territory. Flu vaccines offer “a lot of parallels,” says Tony Yang, a health-policy expert at George Washington University. Again, the two diseases aren’t at all identical. But efforts to vaccinate against either have enough overlap that they can inform each other. Our experience with flu shots reminds us that Americans, cultured to become immune to the notion of unnecessary death from disease, still have a chance to shift that perspective—and chase the kind of immunity that will instead spare them from it.