The judge said the mandate was "arbitrary and capricious" and that it would harm Head Start programs.
The mandate would have required all Head Start employees to be vaccinated against COVID-19.
Head Start is a federal program that provides early childhood education and care to low-income children.The program serves over 1 million children in the United States.
The judge said the mandate would have caused staffing shortages at Head Start programs.
The judge also said the mandate was not based on sound science.
The Biden administration is likely to appeal the judge's ruling.
The ruling is a setback for the Biden administration's efforts to combat the COVID-19 pandemic.
The ruling is also a victory for opponents of vaccine mandates.