A federal judge on Monday blocked key parts of Health Secretary Robert F. Kennedy Jr.'s effort to reshape U.S. vaccine policy, including a move to reduce the number of shots routinely ​recommended for children.

U.S. District Judge Brian Murphy in Boston sided with the American Academy of Pediatrics and other medical groups, which said health regulators had acted unlawfully to carry out Kennedy's agenda of upending immunization policies and warned the changes will reduce vaccination rates and harm public health.

Vaccine makers have grown increasingly wary of U.S. vaccine policy, including the makers of mRNA COVID-19 vaccines Pfizer PFE.N, BioNTech 22UAy.DE, and Moderna MRNA.O. Companies that make other shots on the U.S. childhood vaccine schedule include Merck MRK.N, Sanofi SASY.PA and GSK GSK.L.

As Kennedy's policies have taken hold, pediatricians have faced parents increasingly skeptical about vaccines and medical treatments, while nearly a dozen states have begun considering legal changes that would relax vaccine requirements for school enrollment.

The judge, who was appointed by Democratic President Joe Biden, has earned the scorn of Republican President Donald Trump and his allies for repeatedly blocking administration initiatives, including core parts of Trump's hardline immigration agenda.

The plaintiffs had argued the U.S. Centers for Disease Control and Prevention acted unlawfully when on January 5 it cut the number of routinely recommended childhood vaccinations to 11 and downgraded the immunization recommendations for six diseases, including rotavirus, influenza and hepatitis A.

They also challenged Kennedy's decision last year to remove and replace all 17 independent experts who previously served on the Advisory Committee on Immunization Practices, or ACIP, which makes recommendations that shape U.S. vaccine practices and insurance coverage.

-Nate Raymond/Reuters