Cost effectiveness of adding 7-valent pneumococcal conjugate (PCV-7) vaccine to the Norwegian childhood vaccination program

Abstract

Background

Streptococcus pneumoniae is a frequent bacterial cause of serious infections that may cause permanent sequelae and death. A 7-valent conjugate vaccine may reduce the incidence of pneumococcal disease, but some previous studies have questioned the cost-effectiveness of the vaccine. The aim of this study was to estimate costs and health consequences of adding this pneumococcal vaccine to the Norwegian childhood vaccination programme, taking the possibility of herd immunity into account.

Methods

We developed a simulation model (Markov-model) using data on the risk of pneumococcal disease in Norway, the efficacy of the vaccine as observed in clinical trials from other countries and adjusted for serotype differences, the cost of the vaccine and quality of life for patients with sequelae from pneumococcal disease. The results were expressed as incremental (additional) costs (in euros; €1.00 ≈ NOK8.37), incremental life years and incremental quality adjusted life years. Four different sets of main results are presented: costs and (quality adjusted) life years, with and without indirect costs (the value of lost production due to work absenteeism) and with and without potential herd immunity (i.e. childhood vaccination protects adults against pneumococcal disease).

Results

When indirect costs were disregarded, and four vaccine doses used, the incremental cost per life year gained was €153,000 when herd immunity was included, and €311,000 when it was not. When accounting for indirect costs as well, the cost per life year gained was €58,000 and €124,000, respectively. Assuming that three vaccine doses provide the same protection as four, the cost per life year gained with this regimen was €90,000 with herd immunity and €184,000 without (when indirect costs are disregarded). If indirect costs are also included, vaccination both saves costs and gains life years.

Interpretation/conclusion

In Norway, governmental guidelines indicate that only interventions with cost per life year of less than €54,000 should be implemented. This implies that four dose vaccination is not cost-effective even if decision makers includes both herd immunity and indirect costs in their decisions. If three doses offer the same protection as four doses, however, vaccination would be cost-saving when indirect costs are included, but not with only herd immunity.

Comment

In the autumn of 2005, the Norwegian Government decided to include PCV-7 in the vaccination program. This analysis was used by the Ministry of Health and Ministry of Finance during the decision process.

Introduction

Streptococcus pneumoniae causes septicaemia, meningitis, pneumonia and otitis media world wide. Despite optimal antibiotic treatment the case fatality rate among patients with invasive pneumococcal disease (IPD) remains in the order of 20–30% [1], [2]. IPD is most common among young children and the elderly.

At least 90 different serotypes of pneumococci have been described, based on differences in the antigen structure of their capsular polysaccharides [3]. Since 1984, a vaccine containing 23 different pneumococcal capsular polysaccharides has been available [4], [5], but this vaccine is not recommended for children younger than two years of age because of poor antibody response. In recent years, pneumococcal conjugate vaccines have been developed. Here, the capsular polysaccharides are covalently linked to a carrier protein, and these vaccines induce an immune response even in infants. A 7-valent conjugate vaccine (PCV-7), Prevenar^®, has been tested in large-scale trials in the US [6], [7], [8], [9], [10], and two smaller studies in Europe [11], [12]. The vaccine has not been widely adopted in Europe, possibly because of the high purchasing cost [13], [14], [15], [16], [17] and somewhat conflicting results in otitis media prevention [12]. Recently, UK, The Netherlands and Norway have included the PCV-7 in their vaccination programmes. In the US, where childhood vaccination has been widespread, recent observational studies indicate that the incidence of invasive pneumococcal disease among adults is declining [18], [19], [20], [21].

The aim of this study was to quantify cost and health consequences of adding PCV-7 to the Norwegian childhood vaccination program which includes vaccination at the age of 3, 5, 12 and 15 months. Thus, three or four doses of PCV-7 could be given without any additional visits to the Child Health Clinic. We assumed that vaccination at 3, 5, (6) and 12 months would allow about the same vaccination intervals, and the same immune response, as observed in the clinical trials [6], [11]. Because there is some evidence that even three vaccine doses may offer the same effectiveness as four, [18], [19], [22], [23], [24], [25], [26], [27] and results from immunogenicity studies would support a three dose schedule, we explored this option in additional analyses.