President Donald Trump signed an executive order Monday calling for the measles, mumps and rubella vaccine to eventually be split into three separate shots and for childhood vaccines to be given at separate medical visits.

The order does not immediately eliminate the combined MMR vaccine. Instead, the administration says it wants single-disease alternatives developed while guaranteeing that the combination vaccines remain available.

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The changes are part of the Trump administration's broader overhaul of federal childhood vaccine recommendations, which divides vaccines into three categories:

• Immunizations recommended for all children: measles, mumps, rubella, diphtheria, tetanus, pertussis, polio, Haemophilus influenzae type B, pneumococcal disease, human papillomavirus, and varicella
• Immunizations recommended for certain high-risk groups or populations: respiratory syncytial virus monoclonal antibodies, hepatitis A, hepatitis B, meningococcal B, meningococcal ACWY, and dengue
• Immunizations based on shared clinical decision-making: hepatitis A, hepatitis B, rotavirus, meningococcal disease, influenza, and COVID-19

For parents, the changes could eventually mean more trips to the doctor's office if vaccines that are currently administered together are instead spread across separate appointments.

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The order does not change state vaccination requirements for children attending school. Those requirements are set by individual states. Trump is instead advising states to review their requirements and consider changes based on the federal government's new recommendations.

Dr. Richard Besser, a former acting director of the CDC and longtime pediatrician, sharply criticized the changes in an interview with Scripps News, saying the administration is injecting politics into decisions that should be based on health and science.

"We have to get back to a state where parents can trust the information that's coming from our government, where physicians who are making recommendations to their patients can trust the information coming down," Besser said.

"At this point, I recommend that you do not look at the CDC for vaccine recommendations. Look at the American Academy of Pediatrics," he added. "I'm a member of that organization, and their focus is on children's health, and the vaccine schedule that they put forward makes a lot of sense."

Former CDC chief tells parents not to follow CDC vaccine guidance