A method for preserving an active ingredient comprising the steps of: a) preparing a sample for preservation by dissolving / suspending an active ingredient in a solution of a stabilizing agent； b) subject the sample for preservation to a temperature condition between 5 ° C and 37 ° C and pressure conditions below 2 kPa so that the sample for preservation loses solvent by evaporation, without freezing or bubbling involved in foaming , to form a viscous liquid, in which a viscous liquid is the product of the primary phase of solvent removal； c) further subjecting the sample for preservation to a temperature condition between 5 ° C and 37 ° C and such pressure conditions such that the viscous liquid dries to form a highly viscous liquid in which the pressure is reduced in step c ) compared to the pressure during step b), in which the stabilizing agent comprises a glass-forming polyol, selected from the group consisting of glucose, maltulose, iso-maltulose, lactulose, sucrose, maltose, lactose, sorbitol, iso- maltose, maltitol, lactitol, palatinit, trehalose, raffinose, stachy, melezitose and dextran, in which the concentration of the stabilizing agent used is between 5% and 50% by weight / volume, in which the highly viscous liquid has a solvent content less than or equal to 15% (w / w) and wherein the active ingredient comprises a vaccine comprising a virus.Un procedimiento para conservar un principio activo que comprende las etapas de: a) preparar una muestra para conservación disolviendo/suspendiendo un principio activo en una solución de un agente estabilizante； b) someter la muestra para conservación a una condición de temperatura entre 5 ºC y 37 ºC y unas condiciones de presión por debajo de 2 kPa de manera que la muestra para conservación pierda disolvente por evaporación, sin congelación o burbujeo implicado en la formación de espuma, para formar un líquido viscoso, en el que un líquido viscoso es el producto de la fase primaria de la retirada del disolvente；
