WASHINGTON, D.C. — Senators Bernie Sanders and Bill Cassidy challenged Health Secretary Robert F. Kennedy Jr. over his rejection of germ theory and the effectiveness of vaccines during a hearing of the Senate Committee on Health, Education, Labor, and Pensions on Wednesday. Sanders pressed Kennedy on his past statements disputing that vaccines reduce infant mortality, while Cassidy contested Kennedy's assertions in real time.

"My question is a simple one," Sanders said during the hearing, "do you still believe that one of the central tenets of the germ theory, that vaccines sharply reduce infant mortality, is quote-unquote simply untrue?" Kennedy argued that improvements in nutrition, hygiene, and sanitation, rather than vaccines, accounted for large declines in infant and child deaths during the 20th century. He referenced a 2000 study in the journal Pediatrics with lead author Bernard Guyer. The Guyer study noted that sanitation and other public health strategies introduced in the first half of the 20th century drove major declines in mortality, and that vaccination did not become widely used until after the mid-20th century and thus could not account for mortality declines before that.

Kennedy also said a World Health Organization study was based on modeling in order to discredit it. A 2024 WHO study published in The Lancet found that since 1974, vaccines had saved an estimated 154 million lives, including 146 million children under the age of 5. The organization said vaccines saved the equivalent of six lives every minute of every year over the past 50 years.

Kennedy has no background in science, medicine, or public health and has promoted anti-vaccine views and conspiracy theories. In his 2021 book The Real Anthony Fauci, he wrote explicitly about his germ theory denialism and maligned germ theory as a tool of pharmaceutical companies, scientists, and doctors to promote the use of modern medicines.

Kennedy promotes a concept akin to terrain theory, in which diseases stem from imbalances in the body's inner terrain rather than germs. He claims those imbalances are caused by poor nutrition and exposure to environmental toxins and stressors. His preferred approach emphasizes preventing disease by fortifying the immune system through nutrition and reducing exposures to environmental toxins and stressors, rather than using vaccines or advanced medicines to fight specific pathogens. His Make America Healthy Again movement prioritizes terrain theory over germ theory and promotes healthy diets, lifestyles, and clean living.

As Health Secretary, Kennedy has focused on revamping federal dietary guidance to emphasize whole foods and saturated fat and has criticized artificial ingredients and additives. The 2021 book and his actions as secretary reflect views Kennedy has held and publicly advanced for several years.