August 10, 20262 min read Add Us On GoogleAdd SciAmThe president called for the measles, mumps and rubella (MMR) combined vaccine to be split into separate shots, despite decades of research showing the MMR is safe and effectiveBy Jackie Flynn Mogensen edited by Claire CameronPresident Donald Trump pictured with Robert F. Kennedy, Jr. in 2025 SAUL LOEB/Getty ImagesPresident Donald Trump issued an executive order on Monday aimed at upending the U.S. childhood vaccine schedule. The order would nix the current measles, mumps, and rubella (MMR) combined vaccine in favor of giving each shot individually.A draft of the order obtained by the Washington Post directs Health Secretary Robert F. Kennedy, Jr., to "present plans" to the president to break up the MMR vaccine into its separate constituents. Trump on Monday falsely suggested that for the combined vaccines, "there could be a possibility they’re quite lethal, and separately, it looks like they are not at all lethal, but just very effective." The overwhelming evidence shows that the MMR is both safe and effective with a low risk of adverse events.The draft order directs federal agencies to classify childhood vaccines into three categories: vaccines recommended for all children; vaccines "recommended for certain high-risk groups or populations"; and immunizations given "based on shared clinical decision-making." It's unclear whether the order will have any real effect on the nation's vaccine schedule, which is set by the U.S. Centers of Disease Control and Prevention.On supporting science journalismIf you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.Vaccines in the first group—recommended for all children—include those for measles, mumps, and rubella (MMR), diphtheria, tetanus, and pertussis (DTaP), as well as HPV and polio, among other conditions.Those in the second group, for at-risk populations, include respiratory syncytial virus (RSV) and hepatitis A and B and more, according to the executive order. Among those in the third category, based on decision-making in consultation with a doctor, include hepatitis A and B, COVID-19, influenza and others.Michael Osterholm, director of the Vaccine Integrity Project and an epidemiologist at the University of Minnesota, urged parents in a statement to trust the science. Parents should continue to rely on the evidence-based immunization recommendations developed by trusted medical and public health experts, including the American Academy of Pediatrics. Today's Executive Order does not change the underlying scientific evidence supporting childhood immunization.""We encourage parents to discuss questions about vaccination with their pediatrician or other trusted healthcare provider," Osterholm said.The order is the Trump administration's latest attempt to overhaul and curtail the childhood vaccine schedule. In January, the CDC moved to reduce the number of recommended vaccines for children to protect against 11 diseases; previously, the CDC had recommended children receive inoculations for 17 diseases. That action was blocked by a federal judge in March.This is a breaking news story and will be updated.It’s Time to Stand Up for ScienceIf you enjoyed this article, I’d like to ask for your support. Scientific American has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.I’ve been a Scientific American subscriber since I was 12 years old, and it helped shape the way I look at the world. SciAm always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does that for you, too.If you subscribe to Scientific American, you help ensure that our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the U.S.; and that we support both budding and working scientists at a time when the value of science itself too often goes unrecognized.In return, you get essential news, captivating podcasts, brilliant infographics, can't-miss newsletters, must-watch videos, challenging games, and the science world's best writing and reporting. You can even gift someone a subscription.There has never been a more important time for us to stand up and show why science matters. I hope you’ll support us in that mission.