Correspondence |
The economic cost of invasive pneumococcal disease and the potential for reduction by vaccination in an adult population in South Yorkshire
Sir,Risk factors for invasive pneumococcal disease (IPD) permit targeted immunization of adults with a 23-valent capsular polysaccharide of moderate efficacy.1,2 We identified 553 adult cases of IPD in Sheffield between 1992 and 2000, identified all 230 cases admitted to the Royal Hallamshire Hospital, Sheffield, and retrospectively estimated the economic costs and potential vaccine impact on IPD.
Of 206 cases with analysable medical records, 143 (77%) had prior indications for vaccination per UK guidelines. There were 40 deaths (21%). At our location, 48/50 (96%) strains causing IPD in adults were contained in the pneumococcal polysaccharide vaccine (H.K. Parsons, unpublished data).
The costing took an NHS perspective, including vaccination costs limited to the purchase of the vaccine and the cost impact restricted to the hospital sector. The vaccine price was based on Pneumovax II (Aventis Pasteur MSD). Costs of episodes of IPD were calculated from location and length of stay, with a single out-patient visit assumed. Costs were estimated using national unit data from 2002 assuming average costs (including drug costs) for procedures and medicines.3 To estimate the net present value of the vaccination programme, assumptions were made about uptake, efficacy and longevity of effect and the recommended Treasury discount rate of 3.5% was used.
The 206 patients were hospitalized for 2218 medical bed-days (mean 10.8 days; range 1–63) at £282 per day, and 225 intensive care unit bed-days (mean 11.3 days; range 1–51) at £1274 per day, giving a total cost of £912 126.3 The average cost per patient was £4471. The total in-patient cost of 553 patients with IPD was £2 472 577. Surviving patients (79%) would have received at least one out-patient appointment at a minimum cost of £37 134 (£85 per medical consultation) giving a total of in-patient and out-patient care cost of £2 509 711.3 This gives an annual cost of £278 857 for the city of Sheffield.
The Pneumovax II vaccine costs £9.49. The Sheffield population has 401 200 adults, with 84 100 aged >65 years. We used detailed local estimates for common co-morbidities associated with IPD in the <65 years age group,4,5 factored in that 16% of our cohort had two risk factors, and calculated the total number of individuals requiring vaccination to give a total vaccination cost of approximately £1 228 765.
The results of our analysis of overall net present value are summarized in Table 1. We assumed the cost of IPD in the 23% of individuals without risk factors was not vaccine-preventable. Vaccine efficacy has been estimated to last 6 years.1 Our crude economic analysis has limitations. Incidence of IPD is likely underestimated, since many hospitalized patients do not get blood cultures. We underestimated the number of at-risk patients, but believe the estimate is fairly accurate, since common conditions have accurate local estimates of incidence. We excluded costs of vaccine administration, as most at-risk patients receive yearly influenza vaccination. No estimates of waning immunity with age, decreased efficacy in immunocompromised groups or herd-immunity have been included.
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This analysis highlights the significant hospital cost of IPD in Sheffield, which if representative nationally, could translate to annual savings of £39–90 million (assuming 30–70% efficacy) for England and Wales. The cost per life saved was £7378–37 609, yielding a cost per quality-adjusted life year within the National Institute for Clinical Excellence cost-effectiveness threshold.6
Department of Microbiology and Department of Infection and Tropical Medicine Sheffield Teaching Hospitals Trust Department of Infection and Tropical Medicine Sheffield Teaching Hospitals Trust Health Economics and Decision Science School of Health and Related Research University of Sheffield Department of Infection and Tropical Medicine Sheffield Teaching Hospitals Trust and Division of Genomic Medicine University of Sheffield Medical School Sheffield
email: d.h.dockrell{at}sheffield.ac.uk
References
1. Butler JC, Breiman RF, Campbell JF, Lipman HB, Broome CV, Facklam RR. Pneumococcal polysaccharide vaccine efficacy. An evaluation of current recommendations. JAMA 1993; 270:1826–31.
2. Christenson B, Lundbergh P, Hedlund J, Ortqvist A. Effects of a large-scale intervention with influenza and 23-valent pneumococcal vaccines in adults aged 65 years or older: a prospective study. Lancet 2001; 357:1008–11.[CrossRef][Web of Science][Medline]
3. Netten A and Curtis L. Unit Costs of Health and Social Care 2002; University of Kent at Canterbury.
4. Department of Health. Health survey for England 1995/6; [http://www.doh.gov.uk/public/hs1996].
5. Sheffield Primary Care Trusts. Sheffield Health and Illness Prevalence Survey SHAIPS2 [http://www.sheffield.nhs.uk/shaips].
6. Devlin N and Parkin D. Does NICE have a cost-effectiveness threshold and what other factors influence its decisions? A binary choice analysis. Health Econ 2004; 13:437–52.[CrossRef][Web of Science][Medline]
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