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Republican-led states have filed suits to block a COVID-19 vaccine requirement by the Biden administration that could affect millions of healthcare workers.

Ten states filed suit against the federal government on Wednesday in Missouri. They argue that the vaccine requirement will compound shortages of healthcare workers, particularly in rural areas, and threatens the jobs of "millions" of healthcare workers who put their lives at risk in the initial days of the pandemic.

Last week, the federal Centers for Medicare and Medicaid Services (CMS) required COVID-19 vaccinations for more than 17 million workers at about 76,000 healthcare facilities and home healthcare providers that get funding from the government health programs.

The Biden administration says 2.4 million healthcare workers still require shots.

Similar suits filed by Republican-led states challenge the mandate that requires federal contractors to ensure their workers are vaccinated and that businesses with more than 100 employees require their workers to get vaccinated or wear masks and get tested weekly. All of the mandates are scheduled to take effect Jan 4.

The New Orleans-based 5th US Circuit Court of Appeals last week temporarily blocked the rule, saying it raises "grave statutory and constitutional issues".

In the suit filed with a federal court in St. Louis on Wednesday, the states argue that "compulsory vaccination has always been the province of — and still properly belongs to — the states''.

The lawsuit contends that the CMS vaccine requirement is unprecedented and unreasonably broad, affecting even volunteers and staff who don't typically work with patients.

"The mandate is a blatant attempt to federalize public health issues involving vaccination that belong within the States' police power," said the suit filed by Missouri Attorney General Eric Schmitt, a Republican who is running for the US Senate.

The Biden administration maintains that the federal rules supersede state policies prohibiting vaccine mandates and are essential to slowing the COVID-19 pandemic, which has killed more than 755,000 people in the US.

Joining the lawsuit were the attorneys general of Alaska, Arkansas, Iowa, Kansas, Nebraska, New Hampshire, North Dakota, South Dakota and Wyoming. All are Republicans except for Democratic Attorney General Tom Miller of Iowa, whose state is led by Republican Governor Kim Reynolds. Kansas' governor is Democrat Laura Kelly.

Agencies contributed to this story.