Joe Rogan has challenged vaccine researcher Dr. Peter Hotez to a debate with anti-vaxxer Robert F. Kennedy Jr., offering to donate $100,000 to a charity of Hotez's choice if he agrees. The challenge stemmed from Kennedy's controversial appearance on "The Joe Rogan Experience" podcast where he reiterated his anti-vaccine stance. Hotez responded by suggesting a $50 million endowment for low-cost patent-free vaccines for the world's poor and a public apology from Kennedy. Elon Musk also commented on Twitter, while Hotez invited him to visit his vaccine laboratories and learn more about their work. Kennedy's anti-vaccine views have drawn criticism from his own family members, with his sister calling him "dangerous." He is running as a longshot Democratic primary challenger to President Biden in 2024.