A federal judge in Massachusetts on Monday blocked Health Secretary Robert F. Kennedy Jr.’s recent overhaul of the nation’s childhood vaccine schedule.

The ruling stems from a lawsuit brought by the American Academy of Pediatrics and other medical groups against the Department of Health and Human Services, arguing that Kennedy’s changes to vaccine recommendations and to an influential vaccine advisory committee violated federal law.

In January, Kennedy and the Centers for Disease Control and Prevention made sweeping changes to the childhood vaccine schedule, reducing the number of recommended shots from 18 to 11. The CDC’s change in guidance dropped recommendations that all babies should be protected against hepatitis A, hepatitis B, RSV, dengue and two types of bacterial meningitis.

The judge also put on hold the new members Kennedy appointed to the CDC’s vaccine advisory committee last June. The Advisory Committee on Immunization Practices helps shape U.S. vaccine policy, including recommendations that influence the childhood vaccine schedule and which shots must be covered by insurance.

The panel was scheduled to meet on Wednesday and Thursday. According to the AAP’s attorney, Richard Hughes, the judge’s decision essentially stops that meeting from happening.