A composition comprising (a) Neisseria meningitidis serogroup B outer membranevesicles (OMVs), and (b) an immunogenic component selected from otherNeisseria proteins, or immunogenic fragments thereof. Component (b) preferablyincludes a protein from a different NmB strain from that from which the OMV ofcomponent (a) is derived. The OMVs are preferably obtained by deoxycholateextraction. Optionally, the composition may also comprise a protective antigenagainst other pathogens.