The Morgan Stanley healthcare payor index dropped 1.2 percent.
Wall Street's strong start to the year was fueled by better-than-expected corporate earnings, as well as a compromise in Washington that temporarily averted automatic spending cuts and tax hikes that are predicted to damage the economy.
The compromise on across-the-board spending cuts postponed the matter until March 1, at which point the cuts take effect. Ahead of the debate over the cuts, known as sequestration, further gains for stocks may be difficult to come by.
Some investors say the debate could be the catalyst for a long anticipated sell-off after the market's recent strong run.
Carter Worth, a technical analyst at Oppenheimer, pointed to the "especially complacent action of the past six weeks," noting that, as of Friday, stocks have gone 33 sessions without a dip of more than 1.5 percent.
"We would be selling aggressively into the market's current strength," he said in a research note.
Economic data showed the NAHB/Wells Fargo Housing Market index unexpectedly edged down to 46 in February from 47 in the prior month as builders faced higher material costs.
According to the Thomson Reuters data through Monday morning, of the 391 companies in the S&P 500 that have reported results, 70.1 percent have exceeded analysts' expectations, compared with a 62 percent average since 1994 and 65 percent over the past four quarters.
Fourth-quarter earnings for S&P 500 companies have risen 5.6 percent, according to the data, above a 1.9 percent forecast at the start of the earnings season.
Express Scripts rose 2.5 percent to $56.98 after the pharmacy benefits manager posted fourth-quarter earnings.
About two stocks rose for everyone that fell on the New York Stock Exchange and Nasdaq. About 6.48 billion shares changed hands on the New York Stock Exchange, the Nasdaq and NYSE MKT, in line with the daily average so far this year.