Sanvezzo broke a scoreless tie in the 66th minute when he got control of the ball at midfield, weaved his way into the penalty area, then maneuvered past defender Shaun Francis to launch a right-footed shot into the net.
He doubled the advantage in the 71st minute with a clinical finish after Chicago goalkeeper Paolo Tornaghi came far out of the net to block his first attempt on a breakaway.
Kekuta Manneh also scored for the Whitecaps (9-5-5), who extended their undefeated run to six games and jumped into second place in the Western Conference.
Patrick Nyarko tallied late in stoppage time for the Fire (6-9-3).
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