Disclosed is a peptide that is a molecular mimetic of an epitope of Neisseria meningitidis serogroup B (MenB) capsular polysaccharide (CP) and does not cross-react immunologically with polysialic acid (PSA) of humans, wherein said peptide induces serum bactericidal activity against MenB and comprises an amino acid sequence set forth in SEQ ID No: 2 or 3 (DYAWDDFYYAMGD or DYAWDQTHQ).