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.

Health chief nominee Robert F. Kennedy Jr. wouldn’t deny his long-held skepticism about vaccinations, but he agreed not to discourage parents from vaccinating their children — and that

The fate of Robert F. Kennedy Jr.’s bid to run HHS may rest with a Republican wrestling with his training as a physician and his instincts as a politician.