Infectious disease vaccine business Acambis is to start Phase II trials of its Japanese encephalitis vaccine. This trial is designed to establish the optimum dose and frequency of its ChimeriVax product. Chief executive John Brown said that he was 'delighted that our project is proceeding on schedule and we expect the results to be available around the end of 2001'. Previous trials have showed that prior vaccination against yellow fever does not affect the efficacy of ChimeriVax. The shares picked up 3p on the encouraging news.