The invention pertains to a carrier particle comprising a hydrophilic phase containing a micro-organism and/or subunit thereof, the hydrophilic phase being dispersed in a hydrophobic continuous phase being solid at room temperature, wherein the hydrophobic phase is constituted to undergo a solid-to-liquid conversion at a temperature above room temperature, the conversion comprising a first order transition. The invention also pertains to a pharmaceutical composition comprising said particles, a method for preparation the pharmaceutical composition and the use of this composition in the treatment of an animal.