The present invention provides a simple and cost-effective method of increasing stability and storage time of a protein antigen. This method is used to obtain stable Shigella dysenteriae IpaC protein with higher yield that can be stored for longer duration without changing its secondary structure. The present invention discloses an effective vaccine against Shigellosis which was found to be protective in BALB/c mice against a more than lethal challenge of Shigella flexneri. The primary objective of the present invention is to provide a simple and cost-effective method of increasing stability and storage time of a protein antigen having potential vaccine applications.