Time-to-death is a potential confounder in observational studies of blood transfusion in severe malaria – Authors' reply. Issue 1 (January 2021) - Ackerman, Hans; Olola, Christopher H O; Krishna, Sanjeev; Roberts, David J; Kremsner, Peter G; Newton, Charles R; Taylor, Terrie; Valim, Clarissa; Casals-Pascual, Climent