Fact-Checking the Trump Administration’s Claims About Vaccines

President Trump signed an executive order on Monday calling for scaling back the number of vaccinations American children receive. At an Oval Office event announcing the order, Mr. Trump suggested falsely that vaccines were linked to autism and that the combined measles, mumps and rubella shot could be lethal, among other claims.

While it is not clear yet whether the order has any legal power, experts said they were concerned that the statements from Mr. Trump, Health Secretary Robert F. Kennedy Jr. and others at the event would sow further doubt and confusion about the safety of immunizations.

Here is what the evidence shows on some of those claims.

A combination shot for measles, mumps and rubella is safe and convenient.

Mr. Trump directed health officials to split the measles, mumps and rubella vaccines, which are currently given as a combined product, into three separate shots. “Together, there could be a possibility they’re quite lethal,” he said.

There is no evidence that the combination M.M.R. shot is dangerous, and many decades of evidence for its overall safety. It is associated with a small risk of seizures if a child develops a fever, but that type of seizure — which can occur after any high fever — does not cause long-term harm, according to the Centers for Disease Control and Prevention.

Individual shots for the three diseases are available in some countries, but would need to be tested in the United States before they could be administered. Requiring parents to bring their children in for multiple visits may deter some from getting the required shots.

Splitting the M.M.R. vaccine serves “no medical purpose and would force parents to make multiple appointments, needlessly take time off work and make child care arrangements,” said Dr. Richard Besser, the president of the Robert Wood Johnson Foundation and a former acting director of the C.D.C.

Aluminum is safe and beneficial in vaccines.

The executive order calls for alternatives to the small amounts of aluminum used in some vaccines, which Mr. Kennedy has persistently claimed are unsafe. But aluminum salts, which have been used for nearly 100 years in vaccines to induce a stronger immune response, have been thoroughly studied for safety and efficacy.

Clinical trials conducted over many decades support the use of aluminum. One study published in 2022 suggested a possible association with asthma, but it was small, and the study’s methodology meant it couldn’t show cause and effect. A second study, in Denmark, did not find a link with asthma or any of dozens of other disorders.

A narrower schedule could cause serious harm.

Mr. Trump maintained that “nothing bad can happen from what we’re doing.”

But many diseases have been kept at bay in the United States by high vaccination rates. A study published in 2024 by the C.D.C. found that, for children born from 1994 to 2023, routine vaccinations “prevented approximately 508 million cases of illness, 32 million hospitalizations and 1,129,000 deaths.”

As vaccination rates decline, some of these diseases are coming back, most obviously measles: Less than two-thirds of the way through 2026, there have been more measles cases than in any other year since the disease was declared eliminated in the United States in 2000.

The executive order lists vaccines that it says should only be recommended for high-risk children. On that list are vaccines that protect against several diseases that can be fatal for anyone, including hepatitis A, hepatitis B and meningococcal disease.

The number and volume of childhood shots are not cause for concern.

Mr. Trump emphasized the volume of shots given to children, at various points calling it “the size of a bottle of soda,” “gallons” and “vats of vaccine.” Spacing out shots would “let time elapse between visits so the body can handle this massive amount of fluid being pumped in,” he said.

It is unclear to what Mr. Trump is referring. Most shots contain between 0.25 and 0.5 milliliters of fluid, roughly one-twentieth to one-tenth of a teaspoon.

He and Mr. Kennedy said that American children get 72 shots. In fact, even including vaccines that are recommended and not required, such as a yearly flu shot, children would receive about 35 shots by age 5.

The idea that today’s vaccines are overtaxing children’s immune systems is fundamentally flawed, experts have said. Vaccines today are cleaner and more efficient, and they contain far fewer stimulants to the immune system — by orders of magnitude — than they did decades ago.

Vaccines have been well-studied on their own and in combination.

Stephen Miller, a top aide to Mr. Trump who appeared at the event, said about the childhood vaccine schedule: “Nobody has studied it. Nobody’s looked at it. Nobody’s thought about it.” But for decades, a panel of advisers to the C.D.C. typically spent months or even years reviewing data on new shots before issuing recommendations on which should be given and when.

A federal court in March prevented that committee from meeting, saying the handpicked advisers Mr. Kennedy appointed to replace committee members he had fired were not qualified to make vaccine recommendations.

All vaccines must meet strict requirements for safety before approval. Even after their approval, federal officials monitor reports of side effects in multiple systems that analyze medical records and reports from patients and doctors.

The shots in the schedule have all been closely studied, said Dr. Andrew Racine, president of the American Academy of Pediatrics. “The timing of them and the grouping of them has also been very well studied,” he said.

Studies have shown no link to autism.

Mr. Trump and Mr. Kennedy suggested that the cumulative impact of childhood vaccinations was driving rising rates of autism. While diagnoses have increased over the last several decades, scientists think a confluence of factors may be behind this trend. Those could include people having children later in life, which is associated with a higher risk of autism, as well as more awareness about the condition and a broadening of the diagnostic category to include milder cases.

But dozens of studies have not found a link between vaccines and autism.

Autism experts believe multiple factors, including genetics and possibly environmental influences, play a role in causing autism. Mr. Kennedy has pledged to investigate the “root causes” of autism. Still, federal scientists have not released any new conclusions about what causes the condition.