Use of an observational cohort study to estimate the effectiveness of the New Zealand group B meningococcal vaccine in children aged under 5 years

Int J Epidemiol. 2009 Apr;38(2):413-8. doi: 10.1093/ije/dyn228. Epub 2008 Nov 6.


Background: In July 2004 a strain-specific vaccine was introduced to combat an epidemic of group B meningococcal disease in New Zealand. We estimated the effectiveness of this vaccine in pre-school-aged children.

Methods: We conducted a cohort analysis of all children in New Zealand who were aged 6 months to <5 years at the time the vaccine became available for that age group in their area. We defined cases as children who were diagnosed with laboratory-confirmed epidemic strain meningococcal disease. We calculated person-days-at-risk using data from the National Immunization Register and population estimates from Statistics New Zealand. We estimated vaccine effectiveness as 1--relative risk.

Results: Compared with unvaccinated children, fully vaccinated children were five to six times less likely to contract epidemic strain meningococcal disease in the 24 months after they became eligible to receive a full vaccination series, corresponding to an estimated vaccine effectiveness of 80.0% (95% confidence interval: 52.5-91.6) for children aged 6 months to <5 years and 84.8% (95% confidence interval: 59.4-94.3) for children aged 6 months to <3 years.

Conclusions: With over 3 million doses administered to individuals aged under 20 years throughout New Zealand, combined evidence from the Phase I and II clinical trials, the descriptive epidemiology of meningococcal disease, and this study provide evidence supporting the effectiveness of this vaccine in the 2 years following vaccination.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Child, Preschool
  • Disease Outbreaks / prevention & control
  • Epidemiologic Methods
  • Female
  • Humans
  • Immunization Programs
  • Immunization Schedule
  • Infant
  • Male
  • Meningitis, Meningococcal / epidemiology
  • Meningitis, Meningococcal / microbiology
  • Meningitis, Meningococcal / prevention & control*
  • Meningococcal Vaccines*
  • Neisseria meningitidis, Serogroup B*
  • New Zealand / epidemiology
  • Program Evaluation
  • Treatment Outcome


  • Meningococcal Vaccines