So if not cases, then what? “We need to come to some sort of agreement as to what it is we’re trying to prevent,” says Céline Gounder, an infectious-disease expert at New York University. “Are we trying to prevent hospitalization? Are we trying to prevent death? Are we trying to prevent transmission?” Different goals would require prioritizing different strategies. The booster-shot rollout has been roiled with confusion for this precise reason: The goal kept shifting. First, the Biden administration floated boosters for everyone to combat breakthroughs, then a CDC advisory panel restricted them to the elderly and immunocompromised most at risk for hospitalizations, then the CDC director overruled the panel to include people with jobs that put them at risk of infection.

On the ground, the U.S. is now running an uncontrolled experiment with every strategy all at once. COVID-19 policies differ wildly by state, county, university, workplace, and school district. And because of polarization, they have also settled into the most illogical pattern possible: The least vaccinated communities have some of the laxest restrictions, while highly vaccinated communities—which is to say those most protected from COVID-19—tend to have some of the most aggressive measures aimed at driving down cases. “We’re sleepwalking into policy because we’re not setting goals,” says Joseph Allen, a Harvard professor of public health. We will never get the risk of COVID-19 down to absolute zero, and we need to define a level of risk we can live with…

Once we’ve defined what we are trying to prevent, we can define thresholds for lifting and, if necessary, reinstating COVID-19 measures. This can actually be quite tricky if the goal is minimizing hospitalizations, a lagging indicator that gives you a picture of the past rather than the present. By the time hospitalizations start to rise, a bigger increase may already be baked in with people already infected but not yet sick enough to see a doctor. What to track instead?