Where the data are deficient: a field evaluation of the effectiveness of pneumococcal vaccination in remote Australia

The aims of the study were to: (i) determine whether a field evaluation of a pneumococcal vaccination program conducted in 1991-1993 could show whether the program was effective; and (ii) to describe the epidemiology of invasive pneumococcal disease using laboratory surveillance data. As part of quality assurance, we undertook a retrospective cohort study to compare the hospitalisation and mortality rates of a pneumococcal-vaccine-vaccinated and an unvaccinated group and a correlational study to compare the before- and after-vaccination hospitalisation rates for the vaccinated and unvaccinated groups. We used laboratory data to describe the epidemiology of invasive pneumococcal disease. The cohort study consisted of 815 subjects (306 vaccinated, 509 comparison). No significant differences were observed in the admission rates for pneumonia and lower respiratory tract infection between the two groups. By using a correlational study, we examined before- and after-vaccination hospitalisation rates and this also failed to reveal any differences, except for persons aged 50 years and older. Laboratory surveillance of invasive disease demonstrated that children younger than 6 years and adults younger than 50 years with alcohol-related problems accounted for most of the cases. Despite the study's limitations, it supports the use of pneumococcal vaccine in persons aged older than 50 years, while at the same time highlighting the ongoing need for better vaccines, especially for children and those aged younger than 50 years with medical conditions predisposing to pneumococcal disease.