Being vulnerable to infection even after inoculation is “very scary and frustrating” for immunocompromised people, said Dr. Dorry Segev, a transplant surgeon at Johns Hopkins University who led the study. “They have to continue to act unvaccinated until we figure out a way to give them better immunity.” But in the United States, there is no concerted effort by federal agencies or vaccine manufacturers to test this approach, leaving people with low immunity with more questions than answers. The Centers for Disease Control and Prevention, the Food and Drug Administration and the National Institutes of Health in fact recommend even against testing to find out who is protected. And academic scientists are stymied by the rules that limit access to the vaccines... An infusion of monoclonal antibodies may help some people who don’t produce antibodies on their own — but again, the idea is not being thoroughly explored, said John Moore, a virologist at Weill Cornell Medicine in New York. Use of monoclonal antibodies “makes great sense for this group of people, so I would like to see the companies be more active in this area,” he said. “Government support or pressure would also help.”