Los Angeles: Fifteen Democratic-run US states announced Tuesday they are suing President Donald Trump's administration over its reduction in the number of recommended pediatric vaccines, which they criticise as contrary to science.

The reform, announced in January by the US Department of Health and Human Services, led by long-time vaccine sceptic Robert F. Kennedy Jr, means the country is no longer recommending that every child receive immunisations against several diseases, including rotavirus, influenza and Covid-19.

Instead, the seven vaccines in question are being recommended only for those children at particular risk, a move that upends years of scientifically backed recommendations that reduced disease with routine shots.

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"Secretary RFK Jr. and his CDC (Centres for Disease Control and Prevention) are flouting decades of scientific research, ignoring credible medical experts, and threatening to strain state resources and make America's children sicker," California Attorney General Rob Bonta, leading the lawsuit with his Arizona counterpart, said at a press conference.

Kennedy is named as a defendant, along with the CDC and the Department of Health and Human Services.

The other vaccines stripped of their universally recommended status are for hepatitis A, meningococcal disease, respiratory syncytial virus (RSV) and the highly infectious hepatitis B virus.

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Washington's reorientation of the childhood vaccination schedule has raised concerns within the medical community.

The Trump administration justified its actions last month by saying it was putting the US vaccination policies more in line with those of other countries, citing Denmark as an example.

Some health experts point to Denmark as being a small, homogeneous country with a low prevalence of disease and a centralised health care system that guarantees universal access to care.

Such conditions do not apply to the United States, where the largely privatised health care system is less comprehensive than in northern Europe and has left millions of Americans uninsured.

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"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," Arizona Attorney General Kris Mayes said at the press conference.

Vaccine scepticism has risen in the United States since Trump returned to the presidency 13 months ago.

Vaccination rates have been declining since the Covid pandemic, raising fears of a resurgence in deadly and contagious diseases like measles.

The issue has become deeply political, with California Governor Gavin Newsom, a fierce Trump critic and potential 2028 presidential candidate, weighing in.

"California is going back to court because the Trump administration is violating federal law and pushing a reckless, unscientific childhood vaccine schedule that puts kids' lives at risk," Newsom said in a statement.

The 58-year-old Democrat said undermining confidence in vaccines will lead to lower vaccination rates and more cases of infectious disease.

Other states filing the lawsuit include Colorado, Michigan, New Jersey and Wisconsin.