Early in the pandemic, when vaccines for the coronavirus were still just a glimmer on the horizon, the term “herd immunity” came to signify the endgame: the point when enough Americans would be protected from the virus so we could be rid of the pathogen and reclaim our lives.

Now, more than half of adults in the United States have been inoculated with at least one dose of a vaccine. But daily vaccination rates are slipping, and there is widespread consensus among scientists and public health experts that the herd immunity threshold is not attainable — at least not in the foreseeable future, and perhaps not ever.

For years, scientists and doctors have treated vaccine skepticism as a knowledge problem. If patients were hesitant to get vaccinated, the thinking went, they simply needed more information.

But as public health officials now work to convince Americans to get Covid-19 vaccines as quickly as possible, new social science research suggests that a set of deeply held beliefs is at the heart of many people’s resistance, complicating efforts to bring the coronavirus pandemic under control.

“The instinct from the medical community was, ‘If only we could educate them,’” said Dr. Saad Omer, director of the Yale Institute for Global Health, who studies vaccine skepticism. “It was patronizing and, as it turns out, not true.”