Postbiotics as promising oral vaccine adjuvants

For decades, vaccines have been a key tool against microbial infections. However, the high cost of production and purification renders vaccines largely inaccessible to many developing countries. The limitations of conventional vaccines can be overcome by edible vaccines. To produce an oral vaccine, favourable vectors, such as plants and probiotics, are used. Recent studies have revealed the immunomodulatory effects of probiotics. To improve the efficacy of these vaccines, several adjuvant approaches have been employed. Postbiotics can be used as promising therapy for preventing infections and enhancing the host immune system due to their unique biochemical and microbial-derived properties. In this review, we discuss the feasibility of postbiotics as adjuvants for oral vaccines, highlighting their mechanisms of action, safety profile, and potential to enhance both mucosal and systemic immune responses.