A group of 15 states is suing the Trump administration over recent changes to federal vaccine guidelines for kids.
The lawsuit, announced this week, aims to reverse a decision made in January that reduced the number of diseases kids are routinely vaccinated against from 17 to 11.
The suit also challenges the removal and replacement of the federal panel that advises on vaccine safety and timing.
The case was filed by 14 state attorneys general and the governor of Pennsylvania.
It names the U.S. Department of Health and Human Services, Health Secretary Robert F. Kennedy Jr., the U.S. Centers for Disease Control and Prevention (CDC), and its acting director, Dr. Jay Bhattacharya, as defendants.
"HHS Secretary RFK Jr. and his CDC are flouting decades of scientific research, ignoring credible medical experts, and threatening to strain state resources and make America's children sicker," Rob Bonta, California's attorney general, said at a news briefing.
"The fact is, vaccines save lives and save our state's money," he added.
The lawsuit argues that the new vaccine schedule was not based on any scientific evidence and, instead, copied policies from countries that are far different from the United States.
The updated schedule closely resembles that of Denmark, a country with a much smaller population and a national healthcare system.
"Copying Denmark's vaccine schedule without copying Denmark's health care system doesn't give families more options — it just leaves kids unprotected from serious diseases," Kris Mayes, Arizona's attorney general, told The New York Times.
Another major concern: The changes were announced without review by the federal vaccine advisory panel, known as the Advisory Committee on Immunization Practices (ACIP).
That group has long guided which vaccines kids need and when, and its recommendations help determine what schools require and what insurance will cover.
In June, Kennedy removed all 17 former ACIP members and replaced them with new appointees who share his skepticism about vaccines and mandates.
Since then, the panel has rolled back several long-standing recommendations, including routine hepatitis B vaccination for newborns. Hepatitis B is a highly contagious virus that can cause serious liver damage.
An HHS spokesperson dismissed the lawsuit.
"This is a publicity stunt dressed up as a lawsuit," Emily Hilliard said. "By law, the health secretary has clear authority to make determinations on the CDC immunization schedule and the composition of the Advisory Committee on Immunization Practices."
This lawsuit follows another case filed in July by six major medical groups, including the American Academy of Pediatrics.
That suit challenges Kennedy's decision to stop recommending COVID vaccines for healthy kids and pregnant women.
Those groups argue the changes were "arbitrary and capricious" and bypassed the careful review process normally used for vaccine decisions.
More than 100 public health experts and organizations have filed briefs supporting that case.
A federal judge in Massachusetts heard arguments earlier this month and is expected to rule soon.
The states joining the new lawsuit are Arizona, California, Colorado, Connecticut, Delaware, Maine, Maryland, Michigan, Minnesota, New Jersey, New Mexico, Oregon, Rhode Island, and Wisconsin, as well as the governor of Pennsylvania, The Times said.