Robert F. Kennedy Jr. has been a prominent promoter of vaccine misinformation and public-health conspiracy theories since 2005. His advocacy has included claims about chemtrails, HIV/AIDS denialism, and the assertion of a causal link between vaccines and autism, a claim that has been scientifically disproved. Kennedy founded and formerly chaired Children's Health Defense, an anti-vaccine advocacy group. He has also promoted COVID-19 vaccine misinformation. His work has drawn criticism for contributing to vaccine hesitancy, which has been linked to measles outbreaks in Samoa and Tonga.