Kennedy's statements have raised concerns about his childhood vaccine commitment to Republican Senator Bill Cassidy.

While much of President Trump’s Cabinet has chosen Supreme Court Justice Clarence Thomas to swear them in, Robert F. Kennedy Jr. was sworn in by a different member of the conservative bloc of the court.

But on Tuesday, speaking for the first time to thousands of U.S. Health and Human Services agency employees, he vowed to investigate the childhood vaccine schedule that prevents measles, polio and other dangerous diseases.