Vardy took his tally for the season to 21 goals by ending a five-game drought. The goals sent Leicester 10 points clear of Tottenham ahead of the second-place London club's game against Manchester United.Sunderland is four points from safety with six games remaining.
The hosts held off the leaders until the 66th minute when Vardy met Danny Drinkwater's high ball. The England striker tapped in his second in stoppage time after rounding goalkeeper Vito Mannone.
It appears little can stop Leicester completing its amazing transformation from a team fighting relegation a year ago to lifting the league trophy in May.
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