President Donald Trump's executive order directing that the measles, mumps and rubella vaccine eventually be split into three separate shots — and that childhood vaccines be given at separate medical visits — is drawing sharp criticism from doctors and politicians on both sides of the aisle.

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

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Public health experts say the proposed changes are not backed by science and would create a logistical challenge that could increase the risk of children becoming infected with vaccine-preventable diseases before returning for a follow-up visit.

"This executive order is not really based on science and evidence," Scripps News medical contributor Dr. Omer Awan said. "We know if we take a look at the MMR vaccine that we were just talking about, for example, we know decades of research has shown that this vaccine is safe and effective and splitting it up into individual vaccines or shots is not going to make any of them more safe or more effective."

WATCH | Doctor pushes back on Trump's vaccine executive order

Doctor pushes back on Trump's vaccine executive order

Awan also noted a practical barrier to carrying out the order.

"We currently don't have formulations for the individual measles, mumps or rubella," Awan said. "It exists as a combination vaccine."

The executive order has also drawn pushback from within the Republican Party. U.S. Sen. Bill Cassidy, a physician, said the order would only force children to receive more shots for the same protection the MMR vaccine already provides.

"I'm a doctor. This executive order is wrong," Cassidy said in a statement. "The President does not have the expertise to make these changes. Vaccines are overwhelmingly safe. Vaccines are effective. Vaccines DO NOT cause autism."

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The Trump administration has repeatedly tried to link a rise in autism diagnoses in the U.S. to vaccines. Health experts say there is no data to support that connection and warn that the false information could convince parents to keep their children from getting needed vaccinations.

"The connection between the MMR and autism was raised decades ago by a physician who has been since discredited, and it's been addressed in study after study and there is no connection between the MMR vaccine and autism," said Dr. Richard Besser, former acting director of the U.S. Centers for Disease Control and Prevention. "And the idea that this vaccine is so safe and so effective is now going to get divided into three separate shots. Again, it makes no sense."

Trump's executive order is not law. States, not the federal government, hold authority over vaccine requirements for school-aged children. Trump has also said vaccine decisions will remain up to parents.