About 99 percent of the shares that voted supported the deal, and the deal attracted the support of about 78 percent of all outstanding Coventry shares, Coventry said.
Aetna and Coventry still must get approvals from state insurance regulators and wait for the federal antitrust waiting period to expire before they can consummate the deal, Coventry said.
The companies hope to complete the deal by mid-2013.
Aetna has agreed to pay $5.7 billion in cash and stock for Coventry and assume responsibility for $1.6 billion in notes issued by the Bethesda, Md., health insurer.
Aetna now has 18 million enrollees, 437,000 Medicare Advantage enrollees, 1.2 million Medicaid enrollees, and $36 billion in projected 2012 revenue.
Coventry has 5 million enrollees, 253,000 Medicare Advantage enrollees, 932,000 Medicaid enrollees, and $14 billion in projected 2012 revenue.
Aetna Chairman Mark Bertolini said in a statement that the company welcomes Coventry shareholder approval of the deal.
“We continue to believe that Coventry will complement Aetna’s strategy to expand our core insurance business, increase our presence in the fast-growing government sector and expand our relationships with providers in local geographies,” Bertolini said.