“This is just the result of poor policymaking,” said Richard Hughes IV, a vaccine-law expert at the firm Epstein Becker Green and the former vice president of public policy at Moderna. “I think that vaccines, all vaccines, should be accessible in all settings of care, and so this fragmentation is really just not good.”

“I think this is a reflection of success,” Mr. Hughes said. “We have this brand-new tool to protect infants, and we’ve waited so long to be able to do that.”

Richard H. Hughes IV, a vaccine policy expert and partner at Epstein, Becker & Green, told me that “some insurers have used this language as a way out” by claiming that “may” does not equate a full-throated recommendation. This is a deliberate perversion of CDC’s intention, which was to empower patients to choose what’s best for their individual situations. Instead, that decision is now driven by whether they can pay.

“We sought to emphasize that purchasing insurance that includes coverage of PrEP for HIV in no way burdens the ability of plaintiffs to exercise their religion,” said Richard Hughes IV, the lead attorney for the joint amicus filing by the 25 advocacy groups. “In fact, we suggest to the court that granting exemptions for PrEP coverage would have far-reaching and absurd consequences for our society,” Hughes said.