What is the MMR vaccine and how does Trump’s executive order affect parents and children?

On Monday, Donald Trump signed an executive order pushing for revisions to how children in the US are vaccinated.

The executive order calls for several changes. These include fewer vaccinations overall and a recommendation that the combined measles, mumps and rubella (MMR) vaccine be replaced with separate shots for each disease administered during separate medical visits. The latter direction is currently impossible to implement because no stand-alone shots for these diseases are licensed in the US.

“I think the biggest impact of this executive order is that it’s going to cause more confusion,” says Dr David Diemert, a professor of medicine and director of the George Washington University Vaccine Research Unit. “And confusion for things like vaccination schedules for kids is never a good thing.”

Here’s what you need to know about the executive order’s potential impact and the science behind the debate.

What does Trump’s executive order mean for the vaccine schedule?

Critically, the executive order does not actually “change anything about current recommendations”, says Dr James Campbell, chair of the committee on infectious diseases for the American Academy of Pediatrics (AAP). While the executive order puts pressure on states to change their vaccine policies, it is the Centers for Disease Control and Prevention (CDC) rather than the president that sets federal recommendations.

For now, the proposed changes do not limit access to vaccines or limit insurance coverage.

“Parents should absolutely proceed with getting their child’s vaccines as currently recommended, and explore any questions with their pediatrician,” says Dr Sallie Permar, chair of pediatrics at Weill Cornell Medicine.

Because of the Trump administration’s attempts to change vaccine policy, many states have opted not to follow CDC childhood vaccine recommendations. As of January 2026, at least 28 states, as well as the District of Columbia, announced that they would follow vaccine recommendations from other entities; most of these states indicated they would follow AAP guidance.

Regardless of the executive order, “[the AAP] guidelines will be what we continue to follow. We know these are backed by decades of studies, studying millions of patients, showing the vaccine schedule is safe and effective,” says Dr Katherine Piwnica-Worms, system chief of pediatrics at NYC Health + Hospitals.

This is the latest attempt to change the US childhood vaccine schedule. In March, a court blocked similar changes advocated for by the US health secretary, Robert F Kennedy Jr.

What is the MMR vaccine?

The MMR vaccine protects against three viral infections: measles, mumps and rubella. All three spread easily.

Measles can be serious for all age groups, but can be especially dangerous for babies and young children. In early stages, it’s characterized by a high fever, small spots inside the mouth and a rash. Severe complications, like pneumonia or brain swelling, can lead to hospitalization and death.

While measles was declared eliminated from the US in 2000, cases are now increasing: in August, approximately 2,465 cases were confirmed, a rise linked to slumping immunization rates.

Mumps is another contagious viral infection; symptoms include painful jaw swelling, fever and appetite loss. People who are vaccinated may still get the disease, but can expect milder symptoms and fewer complications.

Though it’s sometimes called “German measles”, rubella is not caused by the same virus as measles. It’s spread through coughs and sneezes, and is especially dangerous during pregnancy for developing babies. One dose of the MMR vaccine is about 97% effective at preventing rubella.

Is the combined MMR vaccine safe?

The CDC currently recommends children get two doses of the combined MMR vaccine.

When signing the executive order, Trump claimed: “Together, there could be a possibility they’re quite lethal, and separately, it looks like they are not at all lethal, but just very effective.”

But the suggestion that the combination vaccine could be “quite lethal” is unsupported by any evidence, says Permar.

“At this point, decades upon decades of data and real-world expertise show otherwise,” she says. The MMR vaccine has been “among the most life-saving of all vaccines”.

There is no evidence that spreading out shots would be safe, according to the AAP. Instead, longer times between vaccinations can leave a child vulnerable to preventable diseases, and multiple shots do not “overwhelm” a child’s immune system.

Do individual vaccines for measles, mumps and rubella exist in the US?

Single shots for measles, mumps and rubella are not available in the US. For them to exist, manufacturers would need to make new lots of the separated vaccines and then test them.

“It would be very costly and take a long time,” says Campbell. “There’s no reason to believe that separating them would have any benefit.”

Why is the MMR a combined vaccine?

The combined vaccine was developed in 1971. Children typically receive their first dose between 12 and 15 months, and their second dose between the ages of four and six years old. The second dose increases the protective immune response to measles and decreases outbreaks of all three diseases overall.

Combination vaccines protect children with fewer shots, and in turn, require fewer appointments. Worldwide, there is an effort to combine more vaccines, says Diemert. “We know that the more injections you include in a schedule, the less likely a child is going to get fully vaccinated,” he says.

Extensive research shows that the MMR vaccine is safe. Careful review of vaccine combinations is also how researchers found that a different combination vaccine called the MMRV vaccine – which also protects against varicella, or chickenpox – is associated with a small increased risk of febrile seizures, says Permar. These brief convulsions are frightening, but don’t cause permanent harm.

In the UK, the MMRV vaccine replaced the MMR vaccine in the National Health Service vaccine schedule. In 2009, the CDC advisory committee on immunization practices (ACIP) updated its guidance to recommend using MMR and a separate varicella vaccine for the first dose, due to the risk of febrile seizures. The AAP recommends either two doses of the MMR or MMRV vaccine.

Does the combined MMR vaccine have any links to autism?

Two dozen studies have found no link between the MMR vaccine and autism, according to the Children’s Hospital of Philadelphia. A 2020 Cochrane Review of the MMR vaccine – considered by the scientific community to be the “gold standard” for high-quality medical information – also found the vaccine to be effective, safe and unrelated to autism.

The original report that suggested the potential link has since been discredited for faulty methodologies.

“There’s never been any data to support that vaccines cause or contribute to autism, but there have been many studies showing no association with autism,” says Campbell.

Further, “there’s better evidence that vaccines can prevent the type of brain damage that may link to autism”, says Permar. For example, contracting rubella during pregnancy can lead to fetal brain damage and an increased risk of autism.

What other vaccines are included in the executive order?

The executive order recommends immunizations for 11 diseases. According to a White House statement, this is a reduction from the 18 diseases recommended by the CDC in 2024.

It also recommends limiting vaccinations for hepatitis A, hepatitis B, influenza, meningitis, respiratory syncytial virus (RSV) and rotavirus to children with a heightened risk of suffering complications from certain illnesses, or to cases in which a healthcare provider and guardian decide vaccination is appropriate, rather than recommending them routinely.

However, scientific evidence suggests all children, not just those in “high risk” categories, benefit from these vaccinations, says Piwnica-Worms.

The proposed limitations to the RSV vaccine especially stood out to Permar, who describes the vaccine as a “success story of American ingenuity”. Research shows that the vaccine made an immediate positive impact after it was approved in 2023, decreasing the number of babies hospitalized from the virus.

Critically, the executive order does not mean there have been any changes to the current vaccine schedule recommendations issued by the CDC. These shots are still recommended to all children.

The AAP’s 2026 childhood immunization schedule also still recommends routine vaccinations against 18 different diseases. The AAP schedule is endorsed by 12 health professional societies.

“The executive order doesn’t change what we need to do in terms of continuing to review vaccine data to help pediatricians and families make good decisions,” says Campbell.

What do experts think of Trump’s executive order on vaccinations?

Declining a vaccination is linked to an increased risk of developing the illness the vaccine is designed to prevent.

But Campbell observes another risk linked to the new executive order: it can cause confusion, leading to lower immunization rates overall. Research suggests that conflicting information, along with misinformation, contributes to declining vaccination rates.

The recommendation to split the MMR vaccine when that is not technically possible could be especially damaging. “I think that may lead some people to think, ‘If I don’t have a choice, then I’m not going to vaccinate,’” says Campbell. “And unfortunately, this is happening in the same year when we’ve had more measles cases since 1991.”

Recent changes and questions to the US vaccine schedule have led to confusion and anxiety in parents, explains Piwnica-Worms. When Kennedy attempted to change the childhood immunization schedule in January, “there was a large rise in questions and hesitancy from families”, she says.

A possible silver lining is that the executive order inspires productive conversations about vaccines, says Diemert, before adding: “I’m struggling to think of a positive.”