Anthem, which has until April 30 to complete its takeover of Cigna to avoid a $1.85 billion termination fee, has vowed to appeal.
Aetna and Humana have both pulled out of multiple states serviced by the Obamacare exchanges, leaving consumers with fewer competitors in the marketplace. The privately run program covers health benefits for 18 million Americans and competes with traditional government-run Medicare, which covers the balance of the 55 million people 65 and older as well as the disabled.
Aetna and Humana haven't yet made a decision to appeal the court order blocking their merger, but Anthem immediately filed an appeal with the U.S. Court of Appeals for the District of Columbia Circuit.
Jackson's decision comes only two weeks after her colleague on the court, Judge John D. Bates, stopped the proposed $37 billion merger of Aetna Inc. and Humana Inc. Federal regulation would likely be "insufficient to prevent the merged firm from raising prices or reducing benefits", Bates ruled. Aetna Chairman and CEO Mark Bertolini said Tuesday that "the current environment makes it too challenging to continue pursuing the transaction" and both companies need to move on.
This August 2011 photo shows the entrance to the Humana building, in Louisville, Ky.
Hartford-Conn. -based Aetna had said it was seriously considering an appeal.
A federal judge blocked the deal last month on antitrust grounds, siding with the Justice Department. They also expect to cut expenses and add customers, which helps them better spread out the cost of investing in technology. The company delayed offering a forecast for 2017, saying that they would provide an update on the proposed $37 billion acquisition by Aetna in a conference call no later than February 16.
Health insurer Anthem has hit back at Cigna after it said it was terminating a merger between the two companies and wants $15bn (£12bn) in fees and damages.