Water-in-mineral oil (W/O) emulsion adjuvants are extensively used for inactivated avian vaccines
formulation. These adjuvants are indeed strong adjuvants that induce long-term efficacy in poultry
vaccines. However, it should be noted that a specific care has to be given to the quality of surfactants as
well as the nature of the oil to avoid safety issues [1]. Whereas W/O adjuvants have mostly been used to
increase humoral immune response, new adjuvants that also increase the cellular immune response could
improve the efficacy of avian vaccines. For example, they could help to extend the vaccinal crossprotection
against different viral strains or serotypes.