Cost-effectiveness of meningococcal polysaccharide serogroups A, C, W-135 and Y conjugate vaccine in Australian adolescents

Abstract

Objectives

The incidence of invasive meningitis disease (IMD) is increasing in Australia. A conjugate vaccine of meningococcal polysaccharide serogroups A, C, W and Y (MenACWY) is currently indicated for infants aged 12 months on the Australian National Immunisation Program. This study sought to determine the cost-effectiveness of a broader MenACWY vaccination program for Australians aged 15 to 19 years.

Methods

A Markov model was constructed to simulate the incidence and consequences of IMD in Australians aged 0–84 years, with follow up until age 85 years. The model comprised four health states: ‘Alive with no previous IMD’, ‘Alive, post IMD without long-term complications’, ‘Alive, post IMD with long-term complications’ and ‘Dead’. Decision analysis compared the clinical consequences and costs of a vaccination program versus no vaccination from the perspective of the Australian health care system. Age-specific incidence of IMD and fatality rates were derived from Australian surveillance data. Vaccine coverage, vaccine efficacy and herd immunity were based on published data. The total cost for MenACWY vaccination was AU$56 per dose. Costs and health outcomes were discounted by 5% per annum (in the base-case analysis).

Results

Compared to no vaccination, a MenACWY vaccination program targeted at Australians aged 15–19 years was expected to prevent 1664 IMD cases in the Australian population aged 0–84 years followed up until age 85 years. The program would lead to 1131 life years (LYs) and 2058 quality adjusted life years (QALYs) gained at a total cost of AU$115 million (all discounted values). These equated to incremental cost-effectiveness ratios of AU$101,649 per LY gained and AU$55,857 per QALY gained. A probabilistic sensitivity analysis demonstrated a likelihood of cost-effectiveness of 34.6%, assuming a willingness to pay threshold of AU$50,000 per QALY gained.

Conclusion

The likelihood of this program being cost-effective under a willingness to pay threshold AU$50,000 per QALY gained is 35%.

Introduction

Invasive meningococcal disease (IMD) is a rare but serious, unpredictable, and life-threatening infectious disease [1]. IMD mostly occurs in children less than five years of age and during late adolescence (15–19 years), with the highest carriage rates in the latter group [2]. Worldwide, there are 13 known serogroups of Neisseria Meningitidis, but serogroups A, B, C, W, X and Y cause almost all cases of IMD [3].

In Australia, since the introduction of the national meningococcal C (MenC) immunisation program for all children and adolescents aged 1–19 years in 2003, the incidence of IMD has decreased drastically, reaching a nadir of 0.6 per 100,000 (149 cases) in 2013 [4], [5]. However, the number of IMD cases has started to increase again since 2014. From 2014 to 2017, the incidence of IMD increased by 167%, reaching 1.6 per 100,000. This increase has been predominantly driven by infections caused by meningococcal W (MenW), which accounted for 37% of all IMD cases in 2017 [6]. MenW is associated with more severe clinical manifestations and a higher case fatality than IMD caused by other serogroups [4], [5]. To curb the increasing trend of IMD, the Australian Federal Government added a conjugate vaccine of meningococcal polysaccharide serogroups A, C, W and Y (MenACWY) (Nimenrix), to the National Immunisation Program (NIP) for infants aged 12 months in 2018 [7]. The government also recently agreed to fund a MenACWY immunisation program for teenagers and young adults, due to the high carriage rate in this population [7]. (At present, there is no national immunisation program against Men B in Australia.) Existing literature suggests the MenACWY vaccination for adolescents in the US, Canada and the Netherlands is cost-effective [8], [9], [10], but there have been no published cost-effectiveness studies from Australia.

In the present study, we estimated the cost-effectiveness, from the perspective of the Australian healthcare system, of a MenACWY vaccination program targeted at Australians aged 15 to 19 years. This work helped to inform the recent decision by the Australian government to fund the program.