A federal vaccine advisory committee plans to review the childhood vaccination schedule and scrutinize vaccines that have been approved for decades, fueling concerns that the panel may consider changes to long-standing vaccine recommendations.

Dr. Michael Ross withdrew from the federal vaccine safety advisory committee Wednesday, two weeks after Health and Human Services Secretary Robert F. Kennedy Jr. appointed him. The Centers for Disease Control and Prevention’s Advisory Committee for Immunization Practices had yet to have its first meeting among the original eight members Kennedy appointed.