Clinical studies have been conducted in New Zealand evaluating the safety and immunogenicity of an outer membrane vesicle (OMV) vaccine, MeNZB, developed to control epidemic disease caused by group B meningococci, subtype P1.7b,4. MeNZB, administered in a three-dose regimen, was well tolerated and induced a seroresponse, defined as a four-fold rise (> or =titre 8) in serum bactericidal antibodies against the vaccine strain 4-6 weeks after the third vaccination, in 96% (95% confidence interval (CI): 79-100%) of adults, 76% (95% CI: 72-80%) of children, 75% (95% CI: 69-80%) of toddlers and 74% (95% CI: 67-80%) of infants receiving MeNZB. In conclusion, these findings suggest that MeNZB is safe and is likely to confer protection against systemic group B meningococcal disease caused by the epidemic strain.