Cost-effectiveness of adolescent pertussis vaccination for the Netherlands: using an individual-based dynamic model

Abstract

Background: Despite widespread immunization programs, a clear increase in pertussis incidence is apparent in many developed countries during the last decades. Consequently, additional immunization strategies are considered to reduce the burden of disease. The aim of this study is to design an individual-based stochastic dynamic framework to model pertussis transmission in the population in order to predict the epidemiologic and economic consequences of the implementation of universal booster vaccination programs. Using this framework, we estimate the cost-effectiveness of universal adolescent pertussis booster vaccination at the age of 12 years in the Netherlands.

Methods/principal findings: We designed a discrete event simulation (DES) model to predict the epidemiological and economic consequences of implementing universal adolescent booster vaccination. We used national age-specific notification data over the period 1996-2000--corrected for underreporting--to calibrate the model assuming a steady state situation. Subsequently, booster vaccination was introduced. Input parameters of the model were derived from literature, national data sources (e.g. costing data, incidence and hospitalization data) and expert opinions. As there is no consensus on the duration of immunity acquired by natural infection, we considered two scenarios for this duration of protection (i.e. 8 and 15 years). In both scenarios, total pertussis incidence decreased as a result of adolescent vaccination. From a societal perspective, the cost-effectiveness was estimated at €4418/QALY (range: 3205-6364 € per QALY) and €6371/QALY (range: 4139-9549 € per QALY) for the 8- and 15-year protection scenarios, respectively. Sensitivity analyses revealed that the outcomes are most sensitive to the quality of life weights used for pertussis disease.

Conclusions/significance: To our knowledge we designed the first individual-based dynamic framework to model pertussis transmission in the population. This study indicates that adolescent pertussis vaccination is likely to be a cost-effective intervention for The Netherlands. The model is suited to investigate further pertussis booster vaccination strategies.

Figure 1. Schematic representation of the possible pathways within the pertussis DES (Discrete Event Simulation) model.

Red circles and red lines indicate events and pathways associated with vaccination, respectively; dashed circles indicate events where no time is actually involved; and shaded circles indicate events where resources are consumed and therefore costs are included.

Figure 2. Age-dependent force of infection (FOI) estimated from the Dutch 1996–2000 pertussis incidence data.

Figure 3. Absolute number of pertussis cases (incidence) for a population 150.000 persons after implementation of booster vaccination at the age of 4 years (t = 0) assuming natural immunity wanes after 15 years.

The situation with adolescent vaccination at t = 10 and the current situation without adolescent vaccination are represented by the red and blue lines, respectively. I₁ = primary infection, I₂ = recidive infection, I₃ = asymptomatic infection and Total = I₁+I₂+I₃. Note the different scales of the y-axis for each infection type.