SACRAMENTO, the United States, Feb. 25 (Xinhua) -- California led a 15-state lawsuit on Tuesday challenging changes to the federal childhood immunization schedule, arguing the revisions are unlawful and could increase disease outbreaks.

California Attorney General Rob Bonta said the new guidance would drive up infectious disease rates and raise Medicaid costs. Arizona Attorney General Kris Mayes joined the suit.

California Governor Gavin Newsom accused the Trump administration of "violating federal law and pushing a reckless, unscientific childhood vaccine schedule that puts kids' lives at risk."

The lawsuit, filed in federal court in Northern California, names Health and Human Services (HHS) Secretary Robert F. Kennedy Jr. and the acting director of the Centers for Disease Control and Prevention (CDC) as defendants.

The states are challenging a Jan. 5 CDC decision that they say downgraded several childhood vaccines from universal recommendations and replaced them with guidance calling for case-by-case discussions between parents and doctors.

The lawsuit also contests Kennedy's dismissal and replacement of the CDC's vaccine advisory committee, arguing the move violated federal law.

The coalition includes attorneys general from 13 other states and Pennsylvania Governor Josh Shapiro.

The states are asking the court to block the revised immunization schedule and invalidate the advisory panel changes.

Oregon Attorney General Dan Rayfield cited an ongoing measles outbreak in his state, with most confirmed cases involving unvaccinated individuals. Wisconsin Attorney General Josh Kaul reported 36 measles cases in late 2025, also among people who were not vaccinated.

An HHS spokesperson told media that the lawsuit was "a publicity stunt dressed up as a lawsuit" and that the health secretary has authority over immunization policy.

California officials said the United States is experiencing its highest measles case numbers in more than three decades, linking the trend in part to declining vaccination rates.