Shares of healthcare and retail giant CVS Health (CVS) - Get Report fell Wednesday following the announcement that Centene plans to buy WellCare - a move seen by investors as a potential hit to revenue at CVS Health's Aetna health insurance business.

Centene (CNC) - Get Report and WellCare (WCG) - Get Report on Wednesday announced they were combining forces in a deal valued at approximately $17.3 billion. The agreement gives the combined company 22 million members across the U.S. and combined 2019 revenue of $97 billion - and bigger scale to compete with the likes of CVS Health's Aetna health insurance business.

CVS in late November officially signed off on its $69 billion mega-merger with healthcare giant Aetna, which combined CVS's pharmacies with Aetna's insurance business and also put CVS near the front of the pack in terms of pharmacy and prescription benefits. 

Centene and WellCare's announcement could potentially affect CVS's position, since the combined companies will directly complete with similar offerings.

To be sure, CVS has its sights on other opportunities in the health care space. 

"The real growth opportunity in that space is in the assisted and the independent living space," CEO Larry J. Merlo said in an interview with TheStreet.com's Jim Cramer on CNBC earlier this week. "We feel that we've got the business stabilized and it'll grow from this point forward."

CVS stock was down 3.1% to $53.69 on Wednesday in trading on the New York Stock Exchange.

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