For months, the number of Americans who opted for their initial doses has held stagnant, at just above 250 million, or about 79 percent of the population. And this last windfall of eligibility seems unlikely to make that number substantially or rapidly budge. A recent Kaiser Family Foundation poll found that less than a fifth of parents are eager to vaccinate their infants and toddlers right away, with the rest unsure about the shots or outright opposed. “I’m usually a much more positive person, but I don’t believe this is going to change much,” says Robin Cogan, a school nurse in New Jersey’s Camden City School District. In her county, just 20 percent of 5-to-11-year-olds have gotten their first two doses.

During the delays in rolling out COVID vaccines for infants and toddlers, doubts about the shots ballooned, and misinformation seeped into data gaps. Parents watched SARS-CoV-2 hopscotch through their families. Now nearly all other mitigation measures—along with much of the fear that clouded the pandemic’s early days and the social incentives that nudged many adults to sign up for shots—have vanished. “Parents are feeling like, if my kids don’t need to be vaccinated in order to go back to school, back to child care, then what’s the point?” Calarco said. The opening up of American society in advance of these vaccines sent a message: The youngest children don’t need to be immunized for things to be all good.

Infant-and-toddler vaccination is now manifesting as yet another symptom of the U.S.’s hyper-individualistic approach to crisis containment—a prioritization of personal choice over collective well-being. Wear a mask or don’t; nab a shot or don’t. Vaccinating the youngest kids will change many little lives, one by one by one. But with so many weights stacked against pediatric vaccination, America will struggle to eke out its biggest benefits for the population at large.