Abstract:
Invasive meningococcal disease (IMD) is a rare but serious infection. A group B IMD epidemic
prompted development of the outer membrane vesicle (OMV) vaccine, MeNZB, which was
delivered to New Zealanders aged 0-19 years from 2004-2008. MeNZB is no longer available
but the new group B vaccine, Bexsero, contains the MeNZB OMVs. Currently, group B causes
approximately half of annual IMD cases in New Zealand.
This research investigated whether MeNZB was effective over the 15 years following
vaccination. A cohort of individuals eligible for vaccination during the immunisation
programme 2004-2006 or in the subsequent period of availability 2006-2008 was identified.
Vaccine effectiveness (VE) of MeNZB was calculated based on the hazard ratio (HR) for
likelihood of hospitalisation for IMD in the years 2004-2018, inclusive, adjusted for age,
gender, ethnicity, geographic location and deprivation.
MeNZB vaccination reduced the likelihood of hospitalisation due to IMD. Adjusted HRs were
0.54 (95% CI 0.47-0.62) and 0.22 (95% 0.14-0.33) after full and partial vaccination (p<0.0001
for both vs unvaccinated), with VE estimates of 46% and 78% after full and partial vaccination,
respectively. Results were similar for the 2004-2006 cohort, indicating preserved effectiveness
despite increased risk of IMD due to young age and high background epidemic pressure.
Regardless of vaccination status, hospitalisation was significantly more likely for young
people, males, Māori, Pacific peoples, those living in the Northern region or with high
socioeconomic deprivation, specifically housing-related deprivation.
MeNZB was not expected to provide sustained protection based on a poorly conserved SBA
response in pre-licensure trials. However, the current findings are consistent with studies of
the Cuban OMV vaccine and Bexsero, which show heterologous protection along with indirect
effects on circulating strains to reduce the overall risk of meningococcal infection. The key
recommendation from this research is the addition of Bexsero to the routine infant
immunisation schedule. This would offer direct protection against IMD and, over time, may
confer indirect protection to reduce the disproportionate burden of infection among vulnerable
groups. A secondary recommendation is for specific policy interventions to reduce household
crowding, which remains a significant risk factor for IMD.