David Cordani, president and CEO of CIGNA Corp., appears on CNBC at the New York Stock Exchange, March 8, 2018.

Cigna and Express Scripts shareholders have approved their merger, rebuking activist investor Carl Icahn and continuing the rapid consolidation in the health-care industry, the companies announced Friday.

In combining Cigna, a health insurer, and Express Scripts, a pharmacy benefit manager, the firms say they can improve care for patients and lower health-care costs. Their rivals are growing and pursuing deals of their own as the industry faces increasing costs and growing political pressure and braces for Amazon's entry.

Icahn opposed the deal earlier this month, arguing that Cigna was overpaying for a company whose business faces possible existential crises from regulators and Amazon. Icahn dropped his fight after influential proxy advisory firms Glass Lewis and Institutional Shareholder Services and hedge fund Glenview Capital Management supported the deal.

Cigna said preliminary results show roughly 90 percent of the votes that were cast backed the deal, while Express Scripts said 99 percent of its shareholders who voted approved the mergers. The final results will be filed with the Securities and Exchange Commission.

After securing shareholders' blessing, Cigna and Express Scripts now need the Justice Department's approval. The agency is also reviewing CVS Health's acquisition of Aetna, a deal that would also combine a pharmacy benefit manager and a health insurer.

CVS executives sounded optimistic about regulatory progress earlier this month. They told Wall Street analysts on an earnings call they now expect the deal to close at the end of the third or beginning of the fourth quarter, a more refined expectation than the previously forecast second half of the year.

Experts have closely watched AT&T's bid for Time Warner for any indications on how the Justice Department may handle these health-care deals. Similar to Cigna-Express Scripts and CVS-Aetna, the deal is an example of vertical integration, where the firms' businesses are similar but do not directly overlap.