LONDON — Canadian doctors have been advised not to use a batch of 170,000 swine flu vaccines after six reports of serious allergic reactions among recipients, but there are no similar reports from other countries, pharmaceuticals company GlaxoSmithKline PLC said Tuesday. Authorities routinely monitor vaccines for any signals of problems, such as the allergic reactions that do occur, rarely, every year. Company spokeswoman Gwenan White said that GlaxoSmithKline advised medical staff in Canada ast week to refrain from using one batch of the vaccine while they look into reports that that it might have caused more allergic reactions than normal....