President Donald Trump issued an executive order two days ago calling for the measles, mumps and rubella vaccine to be split into three separate shots—a move that public health experts say has no scientific basis and could undermine vaccination rates already declining across the country.
Trump claimed without evidence that the combined MMR vaccine could be "quite lethal," but the shot has been proven safe and effective through large-scale studies. Doctors and epidemiologists immediately rejected the assertion. "Completely false," they called it, noting there's no scientific data supporting the separation of the vaccine.
The timing couldn't be worse. The U.S. has logged its highest number of measles cases in decades this year. Roughly 9% of parents already report skipping or delaying the MMR vaccine for their children, according to a 2025 survey by health policy organization KFF and the Washington Post. Dr. Andrew Racine, president of the American Academy of Pediatrics, told reporters that this declining confidence in the MMR shot has directly contributed to the measles resurgence.
The Public Health Cost
Splitting the vaccine would create what public health experts call a self-inflicted crisis. Neil Maniar, a public health professor at Northeastern University, explained the problem bluntly: "They're not solving a problem here. They're creating a new one. Based on false scientific rationale and political ideology, they're changing something that works into something that we have no idea what it will do."
The logistical barriers are substantial. A single MMR shot currently requires one doctor's visit. Separating it into three standalone vaccines would mean six separate doses across a child's early life. For parents already struggling to balance work and healthcare appointments, this creates additional obstacles—especially in rural areas and communities with limited healthcare access. Maniar emphasized that "a single visit can already be challenging for parents who have to take time off work."
William Moss, a pediatrician and epidemiological professor at Johns Hopkins University, highlighted the contradiction at the heart of this proposal. "It's just so counterintuitive and counterproductive," Moss said. "It's ironic when they're claiming that children receive too many shots, and then they turn around and propose a policy that's just going to increase the number of shots they get."
The current childhood vaccination schedule is deliberately designed based on both a child's immune system readiness for each shot and their risk for specific illnesses. Spacing out the MMR components could increase the chance of children missing or delaying protection against preventable diseases they're actually vulnerable to.
Why Manufacturers Won't Comply
Vaccine manufacturers Merck and GSK have little incentive to develop standalone shots. Creating separate vaccines would require significant time and resources diverted from other crucial medical work. "I don't see any world in which vaccine manufacturers have any interest in developing and going through the rigorous regulatory process, getting FDA approval, doing the trials for monovalent measles, mumps, and rubella vaccines," Moss said. "It would be a foolish investment to make." Racine added that developing such vaccines would likely take more than a decade—well beyond Trump's current term.
Merck stated in a Wednesday statement that evidence shows combination shots actually improve childhood vaccination outcomes by increasing completion of all recommended doses and compliance rates.
The Broader Risk
Trump's rhetoric and recommendations could further undermine public confidence in the MMR vaccine's safety, according to Moss. Some experts worry that if states align with new federal guidance, confusion among parents could worsen vaccination hesitancy at precisely the moment measles is resurging.
The origin of Trump's proposal appears traceable to discredited research. A British gastroenterologist named Andrew Wakefield published a paper 28 years ago claiming to show a connection between MMR vaccines and autism. That paper has since been retracted, and Wakefield was removed from the U.K.'s medical register. No credible scientific evidence has ever supported his claims.
Two healthy children died from measles in the U.S. last year. Dr. Racine posed the question directly: "Why would we not give children a vaccine that is safe, that prevents death?"
Maniar stressed the stakes. "We should be doing everything possible to increase those rates rather than implementing policies that present additional barriers to vaccination."
Why This Matters:
This executive order represents a collision between political ideology and public health evidence at a moment when measles cases are at their highest level in decades. The proposal would add barriers to vaccination at a time when vaccination rates are already declining—a contradiction that public health experts say will likely increase disease risk among vulnerable children. The policy relies on claims that decades of safety data have thoroughly debunked, yet the rhetoric alone could further erode parental confidence in proven vaccines. For communities with limited healthcare access—rural areas, low-income neighborhoods—the requirement for multiple doctor's visits creates compounding obstacles. Meanwhile, vaccine manufacturers have no economic incentive to develop these separate shots, meaning any implementation would take over a decade. The immediate consequence is likely increased confusion among parents and continued measles transmission. The longer-term consequence could be a weakening of public trust in vaccination science itself, with effects extending far beyond MMR.