Robert F. Kennedy Jr. ‘s bid to be the nation’s top health official is uncertain after a key Republican joined Democrats to raise concerns over the nominee's skepticism of childhood vaccinations.

Sen. Bill Cassidy has emerged as a central figure in the confirmation of Robert F. Kennedy Jr., whose nomination to health ...

Again and again, Democratic senators pushed Mr. Kennedy to declare that vaccines do not cause autism, a discredited theory that Mr. Kennedy has promoted for years, and save lives. Again and again, he ...