Splitting the MMR vaccine could shrink Colorado parents’ choices, not expand them
Some Colorado parents still wonder whether the vaccines their children receive are necessary, how safe they are and whether the timing of each shot makes sense.
I am a sociologist who has spent nearly two decades studying how parents make vaccine decisions for themselves and their families. I have interviewed dozens of Colorado parents, as well as pediatricians, researchers and policymakers. I have watched vaccine clinics, parent education sessions and meetings of groups skeptical of vaccines. I have also traced the often contradictory information families encounter online, in news coverage and in official documents.
What I hear is not blanket opposition to vaccines. Many Colorado parents say they value independence. They believe they know their children better than physicians or the experts who build vaccine schedules. Their decisions, they say, are tailored to a particular child's needs. That can mean spacing shots or skipping the ones that make them uneasy.
President Donald Trump appeared to be speaking to those parents when he signed an executive order on vaccines on Aug. 10, 2026. The order calls for the components of the combined measles, mumps and rubella vaccine—commonly called the MMR—to be given separately rather than in one shot.
The idea sounds like it offers families more flexibility. In practice, it could make it harder for parents to exercise choice and customize their children's vaccines.
At the signing, Trump repeated an unsubstantiated claim that the combined MMR could be 'quite lethal.' Giving each component separately, he said, would be 'not at all lethal but just very effective.'
The order is largely symbolic, not an implementable policy. But it taps into long-standing parental fears. The notion that giving vaccines one at a time is safer lacks a strong scientific foundation.
A long-standing combination
The CDC recommends that children receive one dose of MMR at 12 to 15 months and a second dose at 4 to 6 years. Because fewer injections are easier on families, the trivalent MMR has been given in combination since 1971 and became the only option around 2008. Its safety record is long, and some evidence suggests the combination may produce a stronger immune response.
According to the CDC, no published scientific evidence shows a benefit from separating the combination MMR into three individual shots.
Nearly a decade ago, while researching my book 'Calling the Shots: Why Parents Reject Vaccines,' I heard parents worry that children receive too many vaccines. They feared the shots could overwhelm a child's immune system or raise the risk of complications. Many did not see every vaccine as equally important for every child.
That view was common. Before the COVID-19 pandemic, between 20% and 25% of U.S. parents chose alternative or slower schedules or rejected some vaccines outright.
Colorado's exemption rate
Colorado law allows parents to opt out of vaccines required for school attendance. Since the pandemic, the number of parents filing exemptions has grown, and Colorado's rate remains above the national average. During the 2025-26 school year, about 87.7% of Colorado kindergartners had received both measles shots. That gave the state the sixth-lowest rate in the country and left it far below the 95% threshold needed for community-wide immunity against measles.
A slower vaccine schedule can sound cautious. Taking things slowly—whether in cars or relationships—generally feels safer.
One mother in my study explained her approach. She accepted vaccines for diseases she 'felt were the most serious and also the ones that had the best track record of (not causing a) reaction.' But she put off vaccines for diseases she did not think her child 'had a high likelihood of catching.' Like many parents, she was not 'anti-vax' or opposed to all vaccines. She wanted to be careful. I withheld her name to protect her privacy.
In my research, I find that parents in general—and mothers in particular—carry a heavy burden when making dozens of choices about their families' health, food, education and care. Vaccines increasingly feel like a high-stakes decision, made harder by confusing and contradictory public health information.
Parents are often overwhelmed by the pressures to gather information to make informed decisions about their children. Fly View Productions/E+ via Getty Images
The supply problem
What seems reasonable in theory can collide with real-world complications. Parents who want to customize a vaccine schedule often cannot do so because of manufacturing and distribution limits.
On one side of the process, no separate shots against measles, mumps and rubella have been manufactured in the U.S. since 2008. Moving from one combined MMR to three individual vaccines would require manufacturers to rebuild the vaccine supply chain.
The MMR has been licensed for decades and is not patented. As a result, the two remaining manufacturers, Merck and GSK, have little incentive to spend millions of dollars and as much as a decade making that change. With many medications already in short supply, it is hard to imagine this becoming a priority.
On the other side, pediatricians already struggle with the cost of supplying and administering vaccines. Estimating demand, preordering doses, insuring shipments and storing shots properly makes vaccination a significant investment and logistical burden for many practices.
Many pediatricians bear the cost burden of providing vaccines to their patients. The Good Brigade/DigitalVision via Getty Images
Some doctors are already rethinking it. One national study found that 36% of pediatricians had considered stopping or had already stopped stocking vaccines. Those who continue may be unable to buy and provide vaccines in multiple forms or store three times as many vials.
That could push more physicians to stop offering vaccines altogether, limiting options and restricting—not expanding—family choice. Some families might find vaccines at county health clinics. Others could be left with no convenient option.
Pharmacists help expand access, but federal law bars them from administering vaccines to children younger than 3, when vaccines are often most important.
Many families could end up unable to get the vaccines they want, especially during outbreaks of the infectious diseases they most fear.
More visits, more barriers
In August 2026, after the executive order, Republican U.S. Sen. Bill Cassidy of Louisiana argued that under separation, 'instead of the child getting two shots, they're getting six. Instead of Mom and Dad missing work twice to bring the child to the doctor, they're missing six times. And instead of the insurance company paying for two visits, they're paying for six.'
Research shows that in rural Colorado, distance, a lack of evening or weekend appointments and high provider turnover already create barriers to vaccination. Counties on the Eastern Plains—Kit Carson, Cheyenne, Lincoln and Elbert—and many mountain communities already have a measurable shortage of primary care providers.
For the 13% of Coloradans who live in rural communities, getting a primary care appointment can take longer than in urban areas and often requires travel. The Colorado Rural Health Center estimates that the average overall cost for rural patients traveling outside their community to see a provider is $718 per trip, including an average of $235 in lost wages.
Expecting six appointments instead of the two recommended to complete the MMR series could increase the chance that some children miss vaccines and remain unprotected.
Healthcare costs are already a barrier. Recent data suggest that almost half of U.S. adults say it is difficult to afford healthcare.
Trump's August executive order does little to help Colorado families who are struggling to make healthcare decisions for their children. Although it promises greater safety, it offers no data, evidence or practical access that would improve children's health or families' lives. The confusion now emerging does little to ease parents' anxiety about the existing vaccine schedule.
This article is republished from The Conversation, a nonprofit, independent news organization bringing you facts and trustworthy analysis to help you make sense of our complex world. It was written by Jennifer Reich, University of Colorado Denver.
Read more:
Vaccine-skeptical mothers say bad health care experiences made them distrust the medical system
Executive order on vaccines bypasses an evidence-based process that has kept kids safe
Federal judge temporarily blocks RFK Jr.'s vaccine agenda—an epidemiologist answers questions parents may have
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