Pneumococcal vaccination and revaccination in the elderly population.

Pneumococcal disease remains a major cause of morbidity and mortality among elderly persons. Invasive infections including bacteremic pneumonia and meningitis are responsible for tens of thousands of hospitalizations and thousands of deaths in this age group each year. According to estimates from the Centers for Disease Control and Prevention, in the United States in 2008 approximately one-third of the 44,000 cases of invasive pneumococcal disease occurred among elderly persons, whereas more than one-half of the 4500 deaths were in this age group [1]. Vaccination with the 23-valent pneumococcal polysaccharide vaccine (PPSV23) is recommended as a critical component of efforts to reduce this burden of invasive pneumococcal disease (IPD) among elderly persons [2]. PPSV23 induces a significant, serotype-specific antibody response in most elderly persons receiving the vaccine for the first time, although certain subgroups (including those with very advanced age and those with serious comorbidities or higher frailty scores) may have diminished immune responses to the vaccine [3]. Vaccination has also been found to be safe and efficacious. In a recent update to a Cochrane Collaboration systematic review , overall pneumococcal polysaccha-ride vaccine efficacy against invasive pneu-mococcal disease among adults from the 10 randomized, controlled trials included in the study was found to be 74% (95% confidence interval [CI], 56%–85%). For the subgroup of otherwise healthy adults in high-income countries (most of whom were older or institutionalized adults), vaccine efficacy was 80% (95% CI, 59%– 90%). The authors also conducted an analysis of 5 observational studies that assessed pneumococcal vaccine effectiveness among immunocompetent older adults, with a pooled vaccine efficacy estimate of 68% (95% CI, 53%–78%) [4]. Although PPSV23 can protect against invasive pneumococcal disease, the duration of this protection may not be long-lasting. Antibody levels following initial vaccination in the elderly decline over time [3] and may approach prevaccination levels after ∼5 years [3, 5]. Furthermore, results from a large observational study suggested that clinical protection also declines over time. In this study of 1054 persons with laboratory documented IPD and 1054 matched controls, polyvalent pneu-mococcal vaccine effectiveness tended to vary both by increasing age and time since vaccination. For the 64–74-year age group, vaccine efficacy was 80% (95% CI, 51%– 92%) for !3 years since vaccination but only 58% (95% CI, Ϫ2% to 83%) for 15 years since vaccination. For persons aged у85 years, vaccine efficacy was 46% (95% CI, Ϫ31% to 78%) for !3 years since vaccination and …