SYDNEY (Reuters) -Australia's Sigma Healthcare shareholders approved in a vote on Wednesday a merger with Chemist Warehouse to create an A$8.8 billion ($5.50 billion) pharmacy and retailing giant. The decision ends more than a year of deliberations between Sigma, Chemist Warehouse and regulators, which had raised antitrust concerns before giving the green light for the transaction in early November. Sigma will pay the privately held Chemist Warehouse shareholders A$700 million in cash as well as stock to facilitate what would effectively be a backdoor listing of the company on the Australian Securities Exchange (ASX).