A federal judge dealt a blow to the Trump administration’s public health agenda on Monday, blocking implementation of an advisory panel’s controversial changes to the childhood vaccine schedule and casting doubt on the panel’s validity.

Judge Brian Murphy of the U.S. District Court for the District of Massachusetts issued a preliminary injunction that halts the changes until he can rule on the merits of a lawsuit brought forward by the American Academy of Pediatrics and other medical groups. The panel was scheduled to meet this week, but the ruling stipulates it may not convene.

Murphy said plaintiffs challenging the changes are likely to succeed in their argument that appointments to the advisory panel violate the Administrative Procedure Act.

At issue are recommendations by the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices that were eventually adopted by the agency. The vaccine advisers, chosen by Health and Human Services Secretary Robert F. Kennedy Jr., voted last year to no longer recommend the hepatitis B birth dose immunization and in January to stop recommending a combined measles, mumps, rubella and varicella vaccine, favoring instead separate MMR and varicella shots. It also ended a recommendation that everyone receive flu and COVID-19 vaccines.

Murphy, a Biden appointee, said the committee’s move to overhaul the childhood immunization schedule was both a “technical procedural failure” and “an abandonment of the technical knowledge and expertise embodied by that committee.”

The panel had repeatedly caused headaches for some Republicans on Capitol Hill who voted to confirm Kennedy, including Senate Health, Education, Labor and Pensions Chairman Bill Cassidy, R-La., a physician.

In the suit, a coalition of leading medical organizations argue that Kennedy and the Trump administration violated established procedure when replacing all 17 existing panel members with Kennedy’s picks, many of whom are known vaccine skeptics.

“First, of the fifteen members currently on ACIP, even under the most generous reading, only six appear to have any meaningful experience in vaccines — the very focus of ACIP,” Murphy writes in his opinion. Several lack “any expertise or professional qualifications related to vaccines or immunization as required by ACIP’s Charter,” he said.

The agency is expected to appeal the decision.

The ruling, while not final, could cast doubt on Kennedy’s ability to carry out his agenda.

“What I hope it says to parents is, listen to your doctor. Don’t listen to the noise that’s out there,” said Richard Besser, former acting director at CDC and now CEO of the Robert Wood Johnson Foundation. “And hopefully, if this really holds, the noise that’s coming from the Department of Health and Human Services will stop.”