Cost-effectiveness of vaccinating for invasive pneumococcal disease in the elderly in the Lazio region of Italy
Introduction
In the Lazio region, Streptococcus pneumoniae is the main cause of meningitis in people of all ages. In 1998, the overall incidence was 1.1 per 100,000, which increases with age: in people 65 years of age or older the incidence rate was 1.3-times higher [1]. Information about other forms of invasive pneumococcal disease is not readily available: between 1997 and 1999 the annual incidence of community-acquired pneumonia-related hospitalisations was 480 per 100,000 people 65+, but the percentage of these inpatient episodes caused by S. pneumoniae and bacteraemia is not known with certainty [2].
Although the first 14-valent pneumococcal polysaccharide vaccine was marketed in 1978, and since 1983 a 23-valent vaccine has been available in developed countries, their efficacy in reducing morbidity and mortality among elderly people has not yet been proved [3]. The most favourable, although not definitive, results are found in preventing the invasive form of the disease, although the definition of invasive changes from study to study. Nevertheless, some governmental agencies and scientific societies recommend vaccinating people over 64 years of age, and some countries in fact have already begun vaccination campaigns [4]. Although the pneumococcal vaccine is not universally recommended for the elderly in Italy, several experimental vaccination campaigns have been conducted.
Most of the recent economic evaluations assume that only the invasive form of the disease can be prevented [5], [6], [7], [8], or they report separate estimates from alternative hypotheses: (i) protection against pneumococcal pneumonia and bacteraemic illness, or (ii) protection against bacteraemia only [9]. The efficacy of the pneumococcal vaccine is still the main source of uncertainty regarding its use [10]. Moreover, due to waning immunity, revaccination of elderly people after 5 years also may be required.
The objective of the present study was to estimate the cost-effectiveness of a hypothetical vaccination campaign among 65+ year olds in the general population in the Lazio region (Italy). Cost-effectiveness was expressed as net healthcare costs per invasive pneumococcal disease (IPD) episode averted and life-year gained (LYG).
Section snippets
Model
The model simulates the healthcare costs and health benefits of carrying out a pneumococcal vaccine program for people over 64 years old in the Lazio region. A cohort of elderly people, identified from official regional demographic statistics as of January 1, 2002, was followed over 5 years. Epidemiological parameters included incidence and case fatality rates of bacteraemic pneumococcal pneumonia and pneumococcal meningitis. Since randomised controlled trials and meta-analyses have not yet
Results
Baseline epidemiological parameters estimated from the Lazio region HIS data are reported in Table 1. Pneumococcal pneumonia incidence was corrected for underreporting. Since no pneumococcal meningitis episodes were recorded among people over 84 years of age between 2001 and 2003, incidence and case fatality in this age group were extrapolated from data on people less than 85 years of age. The estimated overall incidence of bacteraemic pneumococcal pneumonia and meningitis among the elderly
Limits and methodological remarks
Since the perspective of the economic evaluation was that of the health care provider, we included only direct medical costs. That is, we disregarded indirect costs from losses in patient productivity, which consist mostly of missed work, since the target population is over 64 years of age, and the additional costs of professional caregivers. The inclusion of direct costs for care-giving and indirect costs related to patient and caregiver productivity losses would give cost-effectiveness
Acknowledgements
The authors wish to thank Margaret Becker for the English editing, and the personnel at the Communicable Disease Unit and the Hospital Information System Unit of the Public Health Agency of the Lazio region, in particular Fabrizio Perrella, Maria Paola Guerra, Eliana Ferroni, Laura Alecci, Paolo Papini, Valeria Tancioni, Riccardo Salvatori.
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