Kennedy Jr. became the country's top health official, the Centers for Disease Control and Prevention has already pulled back some of its efforts to protect Americans with safe, lifesaving vaccines. The agency has indefinitely postponed a public meeting of its vaccine advisory committee and killed a campaign promoting seasonal flu shots.

Kennedy Jr. told a room packed with federal health workers on Tuesday that he plans to "investigate" whether the timing of childhood vaccinations and anti-depression medications are among several "possible factors" in the nation's problem with chronic diseases.