California has filed a 15-state federal lawsuit challenging recent changes to the U.S. childhood immunisation schedule, arguing the revisions are unlawful and could fuel outbreaks of infectious diseases.

California attorney general Rob Bonta announced the legal action, warning that the new guidance could increase disease transmission and drive up Medicaid costs.

Arizona attorney general Kris Mayes joined the suit, along with officials from 13 other states and Pennsylvania Governor Josh Shapiro.

California Governor Gavin Newsom criticised the administration of President Donald Trump, accusing it of “violating federal law and pushing a reckless, unscientific childhood vaccine schedule that puts kids’ lives at risk”.

Filed in federal court in Northern California, the lawsuit named the U.S. Health and Human Services Secretary Robert F Kennedy Jr and the acting director of the Centres for Disease Control and Prevention are the defendants.

At issue is a January 5 CDC decision that allegedly downgraded several childhood vaccines from universal recommendations to guidance that recommends case-by-case consultations between parents and physicians.

The suit also challenges Mr Kennedy’s dismissal and replacement of the CDC’s vaccine advisory committee, claiming the move violated federal law.

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, likewise concentrated among those who had not received vaccinations.

An HHS spokesperson described the lawsuit as “a publicity stunt dressed up as a lawsuit”, asserting that the health secretary has authority over immunisation policy.

California officials said the U.S. is experiencing its highest number of measles cases in more than three decades, attributing the surge in part to declining vaccination rates. 

(Xinhua/NAN)