Republican Sen. Bill Cassidy of Louisiana, a former physician who has spent his career touting the safety of vaccines, will likely determine whether Robert F. Kennedy Jr., a vaccine skeptic, becomes the country’s next Health and Human Services secretary.

Louisiana Senator Bill Cassidy struggled with RFK Jr.'s anti-vaccine history, but supports his goal for a healthier American diet.

Cassidy is expected to challenge RFK Jr. on his vaccine skepticism and views on public health in today's confirmation hearing.