Related: Robert F. Kennedy Jr. worries anti-obesity drugs could 'double insurance costs for employers'

Three Republican senators who had expressed concerns about Kennedy's views on vaccines — Bill Cassidy of Louisiana, Susan Collins of Maine and Lisa Murkowski of Alaska — have said that Kennedy told them he would maintain current U.S. Centers for Disease Control and Prevention immunization practices recommendations.

Kennedy is the son of the late Attorney General Robert F. Kennedy and the nephew of the late President John F. Kennedy.

He is a lawyer who worked early in his career for three environmental protection organizations: Riverkeeper, the Natural Resources Defense Council and the Waterkeeper Alliance. He began working with Children's Health Defense, a group that opposes standard children's vaccination recommendations and contends that preservatives in vaccines cause autism, in 2015. He has also questioned the standard COVID-19 vaccination and response efforts.

Other federal health benefits team nominees: The Senate Health, Education, Labor and Pensions Committee was planning to hold a hearing on Lori Chavez-DeRemer, a nominee for another key federal health benefits post — U.S. Labor Secretary — Wednesday. The hearing was rescheduled for Feb. 19.

Trump has nominated Dr. Mehmet Oz, a cardiothoracic surgeon and former television show host, to be the Centers for Medicare and Medicaid Services administrator, and Daniel Aronowitz, a lawyer and head of a benefit plan fiduciary insurance business, to be assistant Labor secretary and head of the Labor Department's Employee Benefits Security Administration division.

Confirmation hearing dates for Oz and Aronowitz and dates for Senate votes on their nominations have not yet been announced.