Impact of pneumococcal vaccination on morbidity and mortality of geriatric patients: a case-controlled study

Background: Infections due to Streptococcus pneumoniae are the major cause of adult community-acquired pneumonia, especially in elderly persons with chronic medical conditions. Despite their well-documented efficacy against bacteraemic disease and deaths in the elderly population, pneumococcal polysaccharide vaccines are still very much underused.

Objective: A retrospective, case-controlled study was performed to investigate the impact of vaccination with a polysaccharide pneumococcal vaccine, together with other risk factors, on the incidence of pneumonia and deaths in patients in a long-stay geriatric hospital.

Methods: Subjects were 1,077 residents in a long-stay geriatric hospital in Vienna, Austria, including 359 patients diagnosed as having pneumonia during the period from July 1996 to October 1998 and 718 control subjects. Two controls resident in the hospital during the same time period were matched for each case according to demographic characteristics, chronic illness, and duration of stay in the geriatric ward. The vaccination status was established for all subjects. A logistic regression analysis was performed to assess the efficacy of vaccination and the impact of other cofactors on disease and death.

Results: In cases and controls, 514 (47.7%) had received a pneumococcal vaccine within 2 years prior to the study. There were no differences in demographic characteristics, underlying medical conditions, or duration of stay in the hospital between vaccinated and non-vaccinated patients. In patients diagnosed with pneumonia, 66% were unvaccinated. Logistic regression analysis showed that vaccination significantly decreased the risk of pneumonia (odds ratio 0.279; p < 0.0001). Of the cofactors tested, only gender (lower risk in males) and diabetes mellitus (higher risk) had any impact on disease risk and vaccine efficacy. There appeared to be a highly significant effect of vaccination, reducing the risk of all deaths (odds ratio 0.269; p < 0.0001) and deaths due to pneumonia (odds ratio 0.331; p < 0.0001).

Conclusion: This study showed that vaccination with a polysaccharide pneumococcal vaccine is effective in all groups of geriatric subjects and has a consequential value for health and well-being of elderly institutionalized patients.