In separate meetings Monday, Aetna and Humana shareholders ratified Aetna's $37 billion acquisition of Humana, according to Aetna CEO and Chairman Mark T. Bertolini.
"We're extremely pleased that the shareholders of both Aetna and Humana have overwhelmingly approved proposals related to our pending Humana acquisition," Bertolini said in a statement. "The complementary combination of our companies brings together Humana's leadership and expertise in the Medicare Advantage business with Aetna's strengths in the large commercial health insurance business."
Aetna said it expects the transaction will be completed in the second half of 2016 pending closing conditions, the expiration of the federal Hart-Scott-Rodino antitrust waiting period, and regulatory approvals.
Close to 100 percent - 99 percent - of Aetna shareholders voted for the issuance of common shares to Humana stockholders in connection with the acquisition, according to Aetna.
In another potential merger, shareholders are expected to vote on Centene's $6.3 billion offer for Health Net, two companies that specialize in government-subsidized health plans.
The Centene deal has already received U.S. Justice Department approval, but the Aetna-Humana deal has not.
Last month, the CEOs of both Aetna and Anthem, which wants to buy Cigna for $54 billion, defended their respective multi-billion dollar merger plans before a Senate Judiciary subcommittee.
The mergers would reduce the number of major health insurance companies to three. There are currently five: Aetna, Humana, Anthem, Cigna and UnitedHealth Group.
The Department of Justice will determine whether the mergers constitute a monopoly or violate antitrust laws.