Updated from Tuesday, Jan. 19

BOSTON ( TheStreet) -- Republican Scott Brown won a special election Tuesday to fill the U.S. Senate seat long held by the late Ted Kennedy, complicating the Obama administration's efforts to pass a health care reform bill.

Brown was leading Democrat Martha Coakley 52% to 47% with 98% of precincts reporting, according to results compiled by the Associated Press. Coakley conceded defeat shortly before 10 p.m. EST. Independent candidate Joseph Kennedy, who isn't related to the late senator, had 1%.

Brown, a state senator, campaigned against the health care legislation. Both the House and Senate already have passed different versions of a health care bill that must be reconciled in a bicameral conference committee. Without the Massachusetts seat, Democrats don't have the 60-vote majority in the Senate that allows them to avoid a Republican filibuster.

On Tuesday, health insurer stocks like Humana ( HUM), UnitedHealth Group ( UNH) and Aetna ( AET) all traded higher as it appeared Brown would win the election.

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This article was written by a staff member of TheStreet.com.