Long before the COVID-19 pandemic, Robert F. Kennedy Jr. was building up a following with his anti-vaccine nonprofit group, Children’s Health Defense, and becoming one of the world’s most influential spreaders of fear and distrust around vaccines.

Now, President-elect Donald Trump says he will nominate Kennedy to lead the Department of Health and Human Services, which regulates vaccines.

Kennedy has long advanced the debunked idea that vaccines cause autism. He has also pushed other conspiracy theories, such as that COVID-19 could have been “ethnically targeted” to spare Ashkenazi Jews and Chinese people, comments he later said were taken out of context. He has repeatedly brought up the Holocaust when discussing vaccines and public health mandates.

No medical intervention is risk-free. But doctors and researchers have proven that risks from disease are generally far greater than the risks from vaccines.

Vaccines have been proven to be safe and effective in laboratory testing and in real world use in hundreds of millions of people over decades — they are considered among the most effective public health measures in history.

Kennedy has insisted that he is not anti-vaccine, saying he only wants vaccines to be rigorously tested, but he also has shown opposition to a wide range of immunizations. Kennedy said in a 2023 podcast interview that “There’s no vaccine that is safe and effective” and told Fox News that he still believes in the long-ago debunked idea that vaccines can cause autism. In a 2021 podcast he urged people to “resist” CDC guidelines on when kids should get vaccines.

“I see somebody on a hiking trail carrying a little baby and I say to him, better not get them vaccinated,” Kennedy said.

That same year, in a video promoting an anti-vaccine sticker campaign by his nonprofit, Kennedy appeared onscreen next to one sticker that declared “IF YOU’RE NOT AN ANTI-VAXXER YOU AREN’T PAYING ATTENTION.”

The World Health Organization has estimated that global immunization efforts have saved at least 154 million lives in the past 50 years.

In a study of verified Twitter accounts from 2021, researchers found Kennedy’s personal Twitter account was the top “superspreader” of vaccine misinformation on Twitter, responsible for 13 percent of all reshares of misinformation, more than three times the second most-retweeted account.

He has traveled to states including Connecticut, California and New York to lobby or sue over vaccine policies and has traveled the world to meet with anti-vaccine activists.

Kennedy has also aligned himself with businesses and special interests groups such as anti-vaccine chiropractors, who saw profit in slicing off a small portion of the larger health care market while spreading false or dubious health information.

An Associated Press investigation found one chiropractic group in California had donated $500,000 to Kennedy’s Children’s Health Defense, about one-sixth of the group’s fundraising that year. Another AP investigation found he was listed as an affiliate for an anti-vaccine video series, where he was ranked among the Top 10 for the series’ “Overall Sales Leaderboard.”

His group has co-published a number of anti-vaccine books that have been debunked. One, called “Cause Unknown,” is built on the false premise that sudden deaths of young, healthy people are spiking due to mass administration of COVID-19 vaccines. Experts say these rare medical emergencies are not new and have not become more prevalent.

An AP review of the book found dozens of individuals included in it died of known causes not related to vaccines, including suicide, choking while intoxicated, overdose and allergic reaction. One person died in 2019.

Children’s Health Defense currently has a lawsuit pending against a number of news organizations, among them The Associated Press, accusing them of violating antitrust laws by taking action to identify misinformation, including about COVID-19 and COVID-19 vaccines. Kennedy took leave from the group when he announced his run for president but is listed as one of its attorneys in the lawsuit.