Pneumococcal vaccination of elderly adults: new paradigms for protection

Abstract

Pneumococcal polysaccharide vaccine has been licensed for use in the United States for >30 years, and two-thirds of the elderly population in the United States have received this vaccine. Observational studies have demonstrated that pneumococcal polysaccharide vaccine reduces the risk of invasive pneumococcal disease in immunocompetent elderly individuals, but neither observational studies nor clinical trials have demonstrated consistent evidence for a reduction in the incidence of pneumonia in vaccinated older adults. The introduction of pneumococcal protein conjugate vaccine among children has led to a herd immunity effect that has resulted in a 38% decrease in the rate of invasive pneumococcal disease among elderly adults. The high efficacy of pneumococcal protein conjugate vaccine in children has renewed interest in evaluating pneumococcal protein conjugate vaccines in adults for prevention of invasive pneumococcal disease and pneumonia. Moreover, the recognition of the presence and function of noncapsular pneumococcal protein antigens and the increasing availability of adjuvants highlight the promise of new vaccination strategies to decrease the burden of pneumococcal infection in this high-risk population.

Figure 1.

Pneumococcal polysaccharide vaccine coverage among elderly adults in the United States, 1989–2007. Data adapted from the Behavioral Risk Factor Surveillance System survey [1].

Figure 2.

Risk of invasive pneumococcal disease in elderly adults, by age group and chronic illness category. Blue bars, aged 65–79 years; red bars, aged ≥80 years. Figure adapted from Kyaw et al. [22].

Figure 3.

Pneumococcal vaccine effectiveness against invasive pneumococcal disease by age of recipient and time since vaccination. The point estimate of vaccine effectiveness and 95% CI are indicated. Within each age group, 3 data points represent the vaccine effectiveness at <3 years, 3–5 years, and >5 years since vaccination, from left to right. Data adapted from Shapiro et al. [5].

Figure 4.

Rates of invasive pneumococcal disease in adults ≥65 years of age in the United States, 1997–2006. The 7-valent pneumococcal conjugate vaccine was introduced for children in 2000. Data adapted from the Centers for Disease Control and Prevention Active Bacterial Core Surveillance System [37].

Figure 5.

Geometric mean concentrations (GMCs) of serotype-specific antibodies measured by use of ELISA in adults ≥50 years of age who were observed through their first and second pneumococcal polysaccharide vaccinations. Note that the y-axis scale for serotype 14 differs from that for the other serotypes. Column indicators are defined as follows: A, before first vaccination; B, 4 weeks after first vaccination; C, one year after first vaccination; D, immediately prior to revaccination 4–7 years after first vaccination; E, 4 weeks after revaccination. Data adapted from Torling et al. [43].