The federal court in Massachusetts abruptly halted key components of the overhaul that vaccine skeptic Kennedy has rolled out over the past year, also staying the decisions put forth by the health secretary's hand-picked panel that makes immunization recommendations.

Under Kennedy the US Department of Health and Human Services has announced sweeping changes to the pediatric vaccine schedule, cutting the number of shots universally recommended including for diseases like flu and hepatitis A.

The health secretary additionally stacked a key immunization advisory panel (ACIP) with figures whose anti-vaccine sentiment mirrors his own, having fired the previous members of the influential group.

Several leading medical groups including the American Academy of Pediatrics and the American College of Physicians sued over the policy changes, and on Monday Judge Brian Murphy contended that the organizations were likely to succeed in court on their argument that the shifts were "arbitrary and capricious.".

"There is a method to how these decisions historically have been made -- a method scientific in nature and codified into law through procedural requirements," the judge wrote.

"Unfortunately, the government has disregarded those methods and thereby undermined the integrity of its actions.".

The decision blocks implementation of the recommendations made by the Kennedy-era ACIP committee.

It also said the January memo that upended the childhood vaccine schedule and reduced universal immunization recommendations had not followed proper procedure, as it bypassed the ACIP panel entirely, a move Murphy determined was unlawful.

Health and Human Services spokesperson Andrew Nixon told AFP in a statement that the department "looks forward to this judge's decision being overturned.".

An HHS official told AFP a two-day meeting of the ACIP committee scheduled for this week had been postponed.

The American Academy of Pediatrics called the order "historic and welcome," saying in a statement the changes had "sowed chaos and confusion for parents and pediatricians across the country.".

The health significance of the development depends on confirmed data, public advisories and the response of medical or public-health authorities. Any claim involving risk to patients, medicines, outbreaks or hospital systems should be read alongside official guidance.

For India and other large public systems, such updates are useful when they connect global or national figures with practical questions of access, affordability, prevention, district readiness and communication to vulnerable groups.