Amid the worst US measles outbreak in decades, Health and Human Services Secretary Robert F. Kennedy Jr. returned Thursday to the anti-vaccine advocacy organization he helped create. Kennedy received a standing ovation while delivering the keynote address at the Children’s Health Defense conference.

The outbreak has been driven largely by unvaccinated people. Kennedy’s appearance would have been unthinkable for previous health secretaries and marked a striking return to an organization he left while running for president.

Kennedy spoke between Mark Gordon, president of the MAHA Institute, and Andrew Wakefield, a British gastroenterologist and filmmaker. Gordon called himself the “boldest antivaxxer at an antivax conference.”

Wakefield authored a 1998 study linking vaccination with neurodevelopmental disorders in children, including autism. The study was retracted in 2010, and Wakefield lost his license to practice.

For nearly 40 minutes, Kennedy discussed subjects other than vaccines. He described Trump administration efforts addressing chronic disease through limits on food dyes and access to ultraprocessed foods in government programs, along with an emphasis on regenerative farming.

Kennedy also discussed funding research into possible health harms associated with electromagnetic fields and chemtrails. His mention of chemtrails drew applause from the conference audience.

When Kennedy eventually addressed vaccines, he praised President Donald Trump’s acceptance of vaccine skeptics. Kennedy told attendees, “you have a strong and steadfast friend at the White House.”

“President Trump will not allow the government to treat parents who question vaccine orthodoxies as lepers,” Kennedy said. “We have not taken vaccines away from anyone. We have preserved access, but we have started asking the questions that you and millions of American parents have been asking for years.”

Kennedy, a lawyer, pledged during his confirmation hearing and on social media that he would not restrict vaccine access. During Thursday’s appearance, however, he criticized vaccine safety and effectiveness while promising to continue fighting for people who share his views.

Kennedy helped found Children’s Health Defense and led efforts to file dozens of lawsuits challenging state and federal vaccine policies and public health mandates. The organization also promoted “medical freedom” bills and produced films questioning vaccine safety.

The group’s website offers baby onesies bearing the messages “No Vax No Problem” and “Unvaxxed Unafraid.” Conference attendees could enter a contest for a signed copy of Kennedy’s book “The Real Anthony Fauci” or collect a free copy of “The Wuhan Cover-Up.”

Kennedy called the federal system used to report adverse vaccine related events “very bad.” He said many vaccine injuries are probably “very rare,” but added, “we don’t know, and anybody who tells you that is not talking about science.”

Kennedy mentioned measles only once. The disease was declared eliminated in the United States in 2000, but the country has recorded more than 3,200 cases this year as vaccination rates have declined.

Pennsylvania has reported four measles related deaths this year, including two infants and a person aged 18. Experts say vaccines are highly safe and effective, while vaccine injuries are extremely rare.

A 2021 review examined 338 studies reported across 518 publications. It concluded that vaccines are “safe across populations with serious adverse events being rare, consistent with other recent systematic reviews of vaccine safety.”

As HHS secretary, Kennedy has implemented some of the largest changes to US vaccine policy in decades. Last year, the US Centers for Disease Control and Prevention narrowed its Covid-19 vaccine guidance, saying patients must consult a healthcare provider before receiving the vaccine.

In October, Kennedy created a working group outside the CDC’s traditional advisers to evaluate the safety, effectiveness and timing of vaccines for children and adolescents. He also replaced the CDC’s independent vaccine advisory panel in June 2025.

A judge ruled that the replacement of the panel did not follow federal legal procedures. In a March ruling, US District Judge Brian E. Murphy wrote that “of the fifteen members currently on ACIP, even under the most generous reading, only six appear to have any meaningful experience in vaccines.”

Many of Kennedy’s selected replacements have published or publicly expressed anti-vaccine views. HHS appealed the decision and requested an expedited review.

Kennedy urged Children’s Health Defense members to remain patient with the pace of government change. “We need to measure our success based upon what happens to our kids. That work is far from finished. We’re going to continue to face resistance,” he said.

Kennedy said he intended to remain engaged for as long as he could. He claimed his efforts would restore trust in public health agencies, create a system centered on prevention and end chronic disease.