(1) Invasive infections due to serogroup B meningococci can be life-threatening. Antibiotics are not always effective. Vaccines available in France do not protect against serogroup B meningococci. (2) In the French region of Normandy, a vaccine manufactured by the Norwegian National Institute of Public Health and directed against serogroup B meningococci. (2) In the French region of Normandy, a vaccine manufactured by the Norwegian National Institute of Public Health and directed against a meningococcal strain related to the strain circulating in this region has been used since summer 2006 to protect children over one year of age and adolescents. (3) A review of the 16 available immunogenicity studies shows that immunogenicity is similar in children and adults when the vaccine is administered in two doses, six weeks apart. The manufacturing process was modified in 1995, and the new vaccine could be less immunogenic: three doses provided results similar to those obtained with two doses of the older vaccine. This implies that, in epidemic situations, the maximum protection conferred by the vaccine would be reached 3 to 4 months after beginning vaccination. (4) A double-blind placebo-controlled trial conducted between 1988 and 1991 included 171 800 adolescents aged 14 to 16 years who received two doses of the meningitis B vaccine, or placebo injections. During 29 months of follow-up, 12 invasive infections due to serogroup B meningococci occurred in the vaccine group, versus 24 cases in the placebo group. The protection rate was 57% but the confidence interval was very wide (21% to 78%). A correlation was established between the bactericidal antibody titre and clinical protection. (5) In this trial, the adverse events studied in 877 adolescents were infrequent: less than 4% of local adverse events, and about the same proportion of systemic adverse events (headache, nausea, fatigue, malaise), led to taking time off school. (6) Too few data are available for infants. And it is difficult to extrapolate to other countries the results obtained in Norway 10 years ago with a vaccine that was manufactured differently and may be more immunogenic. (7) In practice, vaccination with the Norwegian vaccine is justified in areas where an epidemic strain closely related to the vaccine strain is circulating, even though only about 60% of vaccinees are protected after three doses.