The main objective of the study is to estimate the proportion of children, born between the 06/04/2004 and the 17/004/2008, living around Neufchatel en Bray, vaccinated by MenBVac, with a serum bactericidal activity against B:14,P1-7,16 clone related to a protection (>= 4), before the first vaccination (T0), after the second MenBvac vaccination (6 weeks after the second vaccination), before the third MenBvac vaccination and after the third MenBvac vaccination (6 weeks after the second vaccination) and one year after the third menBvac vaccination.

Inclusion Criteria:

• children born between 06/04/2004 and 17/04/2008, living in Neufchatel en Bray, vaccinated five times by MenBVac
• parental authority(ies)assent

Exclusion Criteria:

• no parental authority(ies)assent
• no blood sample during the third vaccination
• impossibility of third vaccination
• children with guardianship
• children yet vaccinated or non eligible for vaccination