From MarketWatch:

Some tough talk from President Obama on health-care reform appeared to take a bite out of health-care stocks in Monday afternoon trades, as the sector’s S&P companies dropped nearly half a percentage point.
The biggest loser in Monday trades was also the nation’s largest health insurer, as UnitedHealth Group Inc. /quotes/comstock/13*!unh/quotes/nls/unh (UNH 33.16, -0.58, -1.72%) was down nearly 2%. UnitedHealth shares started to drop as Obama gave his talk around 11 a.m. Eastern time, and stayed down.
But the sector’s losses didn’t multiply as the session wore on. Most companies that lost ground remained steady for the most part.