Surveillance of vaccine breakthrough cases following MeNZB vaccination

To describe and investigate epidemic strain serogroup B meningococcal disease in recipients of the meningococcal vaccine, MeNZB.

Epidemic strain meningococcal disease cases in vaccine recipients were identified by matching disease notification and laboratory data against the National Immunisation Register. Descriptive analyses were undertaken for disease cases aged under 20 years and vaccine breakthrough cases (epidemic strain meningococcal disease cases with onset 28 or more days after receipt of the third MeNZB dose). Questionnaires were sent to hospital clinicians requesting medical histories and laboratory test results for vaccine breakthrough cases. A committee reviewed this information to assess immune competence in these cases.

From the start of the meningococcal B immunisation programme in July 2004 to the end of 2006, 34 vaccine breakthrough cases were identified. No underlying host factors were identified that explained disease occurrence for the 30 cases (88.2%) for whom questionnaires were completed. For 12 (35.3%) cases all requested laboratory tests to assess immune competence were performed and these subjects were judged to be immune competent.

While epidemic strain meningococcal disease incidence has fallen dramatically with the introduction of the vaccine, these early results confirm the expectation that vaccine breakthrough cases will occur in immune competent individuals given the anticipated vaccine effectiveness of approximately 75%.