But on Tuesday, speaking for the first time to thousands of U.S. Health and Human Services agency employees, he vowed to investigate the childhood vaccine schedule that prevents measles, polio and other dangerous diseases.

“Nothing is going to be off limits,” Kennedy said, adding that pesticides, food additives, microplastics, antidepressants and the electromagnetic waves emitted by cellphones and microwaves also would be studied.

Kennedy’s remarks, which circulated on social media, were delivered during a welcome ceremony for the new health secretary at the agency’s headquarters in Washington as a measles outbreak among mostly unvaccinated people raged in West Texas. The event was held after a weekend of mass firings of thousands of HHS employees. More dismissals are expected.

In his comments Tuesday, Kennedy promised that a new “Make America Healthy Again” commission would investigate vaccines, pesticides and antidepressants to see if they have contributed to a rise in chronic illnesses such as diabetes and obesity that have plagued the American public. The commission was formed last week in an executive order by Donald Trump immediately after Kennedy was sworn in as the president’s new health secretary.

That directive said the commission will be made up of cabinet members and other officials from the administration and will develop a strategy around children’s health within the next six months. Kennedy said it will investigate issues, including childhood vaccinations, that “were formally taboo or insufficiently scrutinized.”

While Kennedy did not directly call for changes to the vaccination schedule on Tuesday, his plan to investigate it raises questions about his commitment to Republican Sen. Bill Cassidy, a Louisiana physician who harbored deep misgivings over the health secretary’s anti-vaccine advocacy. Cassidy ultimately voted to send Kennedy’s nomination to the Senate floor after he said Kennedy gave him assurances that he would not alter the federal vaccine schedule.

“On this topic, the science is good, the science is credible,” Cassidy said during a Senate floor speech earlier this month explaining his vote. “Vaccines save lives. They are safe.”

Rigorous studies of thousands of people followed by decades of real-world use have proven that the vaccines approved by the Food and Drug Administration for both children and adults safely and effectively prevent diseases.

Cassidy said during his Senate speech last month that Kennedy had made a number of promises that stemmed from “intense conversations” to garner his support. Specifically, Cassidy said Kennedy would “maintain the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices’ recommendations without changes.”

Those recommendations are what pediatricians around the country use to decide the safest and most effective ages at which to offer vaccinations to children. The committee meets every year to review the latest data on both old and new vaccines to ensure there are no red flags for safety or other issues before publishing its annual schedule.

When contacted about Kennedy’s remarks, Cassidy’s office did not comment.

Kennedy gained a loyal following for his nonprofit by raising objections to COVID-19 protocols and doubts around the COVID-19 vaccine. Despite his work, Kennedy repeatedly told senators that he was not “anti-vaccine” during his confirmation hearings.

Dr. Paul Offit, an infectious-disease expert at Children’s Hospital of Philadelphia who sits on a federal vaccine panel, didn’t believe him.

“I think he will do everything he can to make vaccines less available and less affordable because he’s an anti-vaccine activist,” Offit, who developed the rotavirus vaccine that is on the CDC’s childhood immunization schedule, said last week.

Kennedy promised staffers on Tuesday during his speech that he would keep an open mind in his new job and asked them to return the favor.

“A lot of times when I read these articles characterizing myself, I think I wouldn’t want to work for that guy, either,” Kennedy said, eliciting some laughs from the crowd. “Let’s start a relationship by letting go of any preconceived perceptions you may have of me.”