KATE KELLAND A potential new malaria vaccine has proved highly effective in a trial in babies in Africa, pointing to it one day possibly helping reduce the death toll from the mosquito-borne disease that kills up to half a million young children a year. The candidate vaccine, developed by scientists at Britain's University of Oxford and called R21/Matrix-M, showed up to 77% efficacy in the year-long trial of 450 children in Burkina Faso, researchers leading the trial said in a statement. The scientists, led by Adrian Hill, director of Oxford's Jenner Institute and also one of the lead researchers behind…