Megan Sykes, an immunologist at Columbia University, has spent years using human fetal tissue to develop a mouse with a human-like immune system.

Dr. Adam Bisaga, a professor of psychiatry at Columbia University Medical Center, said it was crucial to combat the ambivalence of many opioid users toward taking medication to ease their addiction.

Dr. Kevin Kalinsky, an assistant professor of medicine at NewYork-Presbyterian Hospital/Columbia University Irving Medical Center, agreed that the new findings are important.

“I think the message is that this is such a serious disease that we need to have something,” said Vincent Racaniello, a professor of microbiology and immunology at Columbia University.