The U.S. passed a major vaccine milestone this weekend, the U.S. Centers for Disease Control and Prevention announced.

More than 180.8 million Americans over 18 are fully vaccinated against COVID-19, which is roughly 70% of adults, according to CDC data released Saturday.

Twenty-two states and the District of Columbia have reached the 70% fully vaccinated threshold among their adult populations as of Saturday afternoon, according to the CDC data. Connecticut leads the U.S. with 82.7% of its residents 18 and older with at least one shot, the data showed.

About 80% of adults, roughly 208 million Americans over 18, have had at least one dose of a coronavirus vaccine, the CDC data showed. Pennsylvania leads the country with 94.3% of adults with at least one dose, the data showed.

A federal appeals court has issued a stay on a Biden administration rule requiring all companies with at least 100 employees to mandate COVID-19 vaccines or implement weekly testing.

The 5th Circuit, based in New Orleans, said it was delaying the federal vaccine requirement because of potential "grave statutory and constitutional issues" raised by the plaintiffs, court documents show.

The government must provide an expedited reply to the motion for a permanent injunction Monday, followed by a petitioners' reply on Tuesday.

Nearly 100 million workers would be required to get the vaccine by Jan. 4, with some allowed to test weekly instead, under federal rules released Thursday.

Since then, five lawsuits involving 26 Republican-led states combined have been filed in federal court. Five states -- Louisiana, Mississippi, South Carolina, Texas and Utah -- filed in the 5th Circuit.

-ABC News' Jason Volack and Chris Howell

Over two dozen states have filed lawsuits aimed at dismantling the Biden administration's COVID-19 vaccine mandate that affects nearly two-thirds of the workforce.

Nearly 100 million workers will be required to get the vaccine by Jan. 4, with some allowed to test weekly instead, under federal rules released Thursday.

Since then, five lawsuits involving 26 Republican-led states combined have been filed in federal court seeking to overturn what they claim is an unlawful mandate.

Seven states -- Idaho, Kansas, Kentucky, Ohio, Oklahoma, Tennessee and West Virginia -- filed a lawsuit against OSHA in the 6th Circuit.

Eleven others -- Alaska, Arizona, Arkansas, Iowa, Missouri, Montana, Nebraska, New Hampshire, North Dakota, South Dakota and Wyoming -- joined together to file a lawsuit against Biden and OSHA in the 8th Circuit.

Five states -- Louisiana, Mississippi, South Carolina, Texas and Utah -- filed a lawsuit against OSHA in the 5th Circuit, and three more -- Alabama, Florida and Georgia -- filed in the 11th Circuit.

The Biden administration has said lawsuits were expected but that the federal government should win in court.

“The administration clearly has the authority to protect workers, and actions announced by the president are designed to save lives and stop the spread of COVID,” White House spokeswoman Karine Jean-Pierre said Thursday.

-ABC News' Cheyenne Haslett

Scientists at Oxford University have identified a gene linked to an increased risk of respiratory failure from COVID-19 in people under 65, offering a new clue that could help scientists develop new treatments for the virus.

Researchers had previously identified a stretch of DNA that increased the risk, though the exact gene responsible, and why that was happening, was unknown. In a study published in Nature Genetics this week, scientists determined the gene associated with the increased risk.

According to the study, 60% of people with South Asian ancestry carry the high-risk genetic signal, which researchers said could partly explain the devastating impact of COVID-19 in India and in some UK communities.

Other major risk factors for severe COVID-19 include medical conditions like obesity, asthma, diabetes and many other chronic diseases.

-ABC News' Sony Salzman