Provided herein is a method for storing an emulsion-adjuvanted vaccine in a medical injection device having a lubricant coating, said method including the steps of: (a) providing a medical injection device having a barrel having an inner surface； (b) forming a silicone oil layer on at least a part of the inner surface of the barrel that is intended to be in contact with the vaccine； (c) carrying out an oxidizing plasma treatment of the layer so as to crosslink at least part of the silicone oil layer and form a lubricant coating； and (d) filling the barrel with the emulsion-adjuvanted vaccine. The invention also relates to a medical injection device obtained directly from this method and to the use of plasma-treated silicone oil as a lubricant coating.
