Abstract: The present invention relates to novel compositions for medical use, particularly for use as vaccines. The present invention relies upon the dependence of the bacteria of the species Alliivibrio wodanis (formerly Vibrio wodanis) in the pathogenesis in the unrecognized, novel disease wodanosis (Norwegian: odinose), as well as in the chronic disease stages of winter ulcer in a composition together with Moritella viscosa (M. viscosa). in addition, it is also related herein to a composition comprising inactivated bacteria of one or more culture(s) of the species M. viscosa cultivated in physical contact with cells of A. wodanis to improve the technical composition and protection of a vaccine against winter ulcer. The invention also relates to use of such vaccine compositions in prevention and/or treatment of wodanosis and winter ulcer, methods for the production of such vaccines, and to methods for preventing, controlling and combating Alliivibno wodanis infection and chronic winter ulcer in fish.