Trump official Dr. Mehmet Oz has risked the ire of the president by refuting his unsubstantiated claims about the safety of the MMR shot and stating it is “not a lethal vaccine.”

The Centers for Medicare and Medicaid Services leader appeared Sunday on CBS News, where he was asked about Trump’s recent remarks that the vaccine, which targets measles, mumps and rubella, “was possibly quite lethal.”

Oz was pressed by anchor Margaret Brennan, and equivocated before finally stating: “No, the MMR vaccine is not a lethal vaccine, and it is offered in other countries.”

The MMR shot, which was introduced in 1971, has helped prevent millions of cases of measles. More than 100 million doses are given on average each year around the world.

The recommended two doses of the shot are 97 percent effective at preventing measles and 86 percent effective against mumps, the Centers for Disease Control and Prevention says. One dose is 97 percent effective against rubella. Without the shots, these infectious diseases can lead to brain swelling, severe infection and death.

Trump caused outrage among hundreds of renowned medical groups after he signed an executive order August 10 that recommended splitting up the MMR vaccine into separate shots.

Along with the baseless claim that the combined shot could be lethal, Trump has also suggested the vaccine is tied to autism.

Health Secretary Robert F Kennedy, Jr, a longtime vaccine skeptic, also claimed this month that a study supporting a link between autism and splitting the MMR vaccine had recently been released. However, the Annenberg Policy Center, a non-profit research center at the University of Pennsylvania, said they could not find such a study while fact-checking Kennedy’s statements.

The U.S. Centers for Disease Control and Preventions states there is “no link between the MMR vaccine and autism,” based on decades of extensive research.

Oz, a former cardiothoracic surgeon, previously came under fire from doctors in 2015 for medical advice given on his popular daytime TV show. CBS News also reported in 2014 that a study about the benefits of green coffee bean extract, promoted on his show, was retracted.

Oz featured Trump on his show when he was first running for president in 2016. He was subsequently nominated by Trump for the high-level public health role in his second term, after he lost a race to become a U.S. senator for Pennsylvania.

The Independent has asked the Department of Health and Human Services for comment.

The uptake of the MMR vaccine in children is currently at lower levels in the U.S. than needed for immunity, and cases of measles are at the highest level in 35 years.

Without the vaccine, mumps and rubella could also make a comeback, although the infections don’t spread as easily as measles.

Splitting the shots could further worsen vaccine hesitancy, experts say, because more shots mean more time and effort spent going to the doctor.

When “vaccines are split and more doses or visits are needed,” Andrew Pollard, director of the Oxford Vaccine Group at the University of Oxford, said. “[T]he result is that doses are missed and protection in the population drops.”

He added: “This is very dangerous in the cases of these viruses, not least with outbreaks of measles already [ongoing].”

That process of splitting the MMR vaccine may take years – along with potential regulatory hurdles and pushback from manufacturers – but Kennedy said the Trump administration would work “as quickly as [it] can.”