Dec 16 (Reuters) - Canada’s main stock index opened higher on Wednesday, helped by gains in gold miners, as optimism around the rollout of coronavirus vaccines and hopes of fresh U.S. stimulus bolstered sentiment. * At 09:32 a.m. ET (14:32 GMT), the Toronto Stock Exchange’s S&P/TSX composite index was up 67.67 points, or 0.39%, at 17,574.15.