Robert Francis Kennedy Jr. (born January 17, 1954), also known by his initials RFK Jr., is an American politician, environmental lawyer, author, conspiracy theorist, and anti-vaccine activist serving as the 26th United States secretary of health and human services since 2025. A member of the prominent Kennedy family, he is a son of Senator and US attorney general Robert F. Kennedy and a nephew of US president John F. Kennedy and US senator Ted Kennedy. Kennedy began his career as an assistant district attorney in Manhattan. In the mid-1980s, he joined two nonprofits focused on environmental protection: Riverkeeper and the Natural Resources Defense Council (NRDC). In 1986, he became an adjunct professor of environmental law at Pace University School of Law, and in 1987 he founded Pace's Environmental Litigation Clinic. In 1999, Kennedy founded the nonprofit environmental group Waterkeeper Alliance. He first ran as a member of the Democratic Party and later started an independent campaign in the 2024 presidential election, before withdrawing from the race and endorsing the Republican Party's nominee, Donald Trump. Since 2005, Kennedy has promoted vaccine misinformation and public-health conspiracy theories, including the chemtrail conspiracy theory, HIV/AIDS denialism, and the scientifically disproved claim of a causal link between vaccines and autism. He has drawn criticism for fueling vaccine hesitancy amid a social climate that gave rise to the deadly measles outbreaks in Samoa and Tonga. Kennedy has said that all his children were vaccinated and, during the 2025 measles outbreak, publicly encouraged people to get the measles vaccine. Kennedy is the founder and former chairman of Children's Health Defense, an anti-vaccine advocacy group and proponent of COVID-19 vaccine misinformation. He has written books including The Riverkeepers (1997), Crimes Against Nature (2004), The Real Anthony Fauci (2021), and A Letter to Liberals (2022). In November 2024, President-elect Trump nominated Kennedy for secretary of health and human services (HHS). In February 2025, the Senate confirmed Kennedy by a vote of 52 to 48, and he was sworn in shortly thereafter amid strong opposition from scientists and medical groups. His tenure has been marked by controversial actions on vaccines, public health policy, and agency leadership that have drawn significant legal, scientific, and political criticism.