The Real Story: Potential impacts of separating MMR Vaccine
President Donald Trump signed an executive order last week aimed at upending 55 years of vaccine best practices.
The order recommends the MMR vaccine - for measles, mumps, and rubella - should be administered to children in three single-disease shots at different medical visits. The order says this to give parents “more options regarding the timing and frequency of this vaccine administration.”
Dr. Mark Fox is the Dean of the Indiana University School of Medicine in South Bend. He says the current combination MMR shot has had a good safety record for more than 50 years.
So, when it comes to potentially dividing up the vaccine, he says there is no benefit.
“There's no benefit from that in terms of additional protection, and there's no benefit in terms of improved safety from dividing the shots that way," says Dr. Fox. "In fact, the individual elements, measles and mumps and rubella, aren't even available in the United States at this point. So, there will be a production period to even generate those as separate shots."
Dr. Fox says these aren’t the recommendations endorsed by the CDC or the American Academy of Pediatrics.
He says there’s a theoretical problem - in that these changes sow confusion and distrust. According to Dr. Fox, a more practical concern related to the division of doses is that it means separate medical visits.
“The likelihood that any family will complete the three visits as scheduled at each step required for full protection against measles, mumps, and rubella just introduces friction that makes it less likely that they will successfully complete the vaccine series. Additionally, any delay that you introduce prolongs a period of vulnerability where a child could get sick and expose others to one of those illnesses,” said Dr. Fox.
Santosh Gautam, PhD, is a professor of global health economics at the University of Notre Dame’s Keough School of Global Affairs.
His research focuses on how health in the first five years of life impacts adult life outcomes, and ABC57’s Jordan Tolbert spoke with him about the MMR vaccine and the impact of vaccines on children’s health and future.
“I'm saying that these vaccines, in addition to improving health, also affect non-health outcomes such as education, human capital, employment, and also lifelong income as well,” said Gautam.
The CDC says measles can cause long-term impacts by damaging the immune system for up to a few years. Other serious complications include brain swelling or a rare but fatal disease of the central nervous system.
Gautam says dividing the MMR shot into three separate visits could cause logistical issues for families.
“There's also equity consideration as well. So, as we know, in the U.S., there's large socioeconomic disparities in terms of completing vaccines for children and separating out vaccines may increase the inequity in terms of access and also completing the vaccines for communities or households from a lower socioeconomic community,” said Gautam.
Gautam says if the MMR vaccine is separated, that could reduce the vaccination rate in the U.S.
According to the most recent data from the CDC for kindergarteners in the 2024-2025 school year, 90.8 percent were vaccinated with the MMR vaccine, and 91.6 percent in Michigan. According to the CDC, there were more than 2500 confirmed cases of the highly contagious virus as of August 13th, 2026, with two cases in Indiana and 15 in Michigan.