The present invention relates to immuno-protected encapsulated cells producing an immunomodulator, for example GM-CSF (granulocyte-macrophage colony stimulating factor). The cells of the invention are particularly well adapted for providing an active adjuvant or immunomodulator, for example in the context of immunization in humans and animals. These cells can be used for vaccination where they provide the immunomodulator in an active form, in a continuous, non-immunogenic manner in the immediate vicinity of the vaccine antigen(s). The invention also relates to a vaccine composition comprising immuno-protected encapsulated cells producing an immunomodulator and an antigenic component. The invention also relates to a kit comprising a cell as described and an antigenic component. The strategy of the invention is perfectly suited for both cancer immunotherapy and vaccination against infectious agents.