While the "vote of confidence" from Buffett's investment validates the long-term value of UnitedHealth shares, the "management needs to regain trust and credibility with investors, and get back to its beat and raise reputation of the past," said James Harlow, senior vice president at Novare Capital Management.

Berkshire Hathaway’s UnitedHealth Group Incorporated investment highlights confidence in healthcare. Click for why I am bullish on UNH stock prospects.

Warren Buffett's Berkshire Hathaway disclosed on Thursday a new investment in UnitedHealth Group after the insurer became a target for many Americans upset over the direction of the nation's healthcare.