Poisson Regression Modelling of the Effectiveness of the Meningococcal B Vaccine (MeNZB)

Purpose

The main objective of this study is to apply a Poisson regression model of epidemic strain Meningococcal B disease rates in New Zealand in order to assess the impact of a new vaccine (MeNZB). The study design of a staged roll-out of the vaccine in different age groups and geographic regions allows for an estimation of the vaccine effect that is not confounded with the progression of the epidemic over time. The Poisson regression model considers the number of subjects at risk, as well as the time at risk, so that the disease rates are calculated as the average number of cases per person per unit of time. This method of estimating rates facilitates the incorporation of the rollout vaccination schedule. The analysis defines cases as individuals with the epidemic strain of meningococcal disease and estimates the effects of vaccination in different age and ethnic groups, while accounting for potential covariates of region-specific disease rates, deprivation, time, and seasonality.