TABLE 1

Summary of clinical and laboratory measurements of antipneumococcal immunity in young and old adults

MeasurementHealthy young adultsOlder adults
Mucosal colonization (culture confirmed)Occurs in up to 10% at any one timeOccurs in <5%
Colonization-associated immune boostingHas been demonstratedHas not been demonstrated
Circulating natural anti-CPS antibody titerRobustDeclines with age
Circulating natural anti-CPS antibody opsonophagocytic activityRobustDeclines profoundly with age
Anti-CPS antibody titer following vaccinationRobustRobust
Anti-CPS antibody opsonophagocytic activity following vaccinationRobustDeclines with age
Memory B cell response to vaccinationConflicting results between different studies; memory B cell responses may be superior in younger adults; hyporesponsiveness to multiple doses of unconjugated polysaccharide seen in all age groups
Clinical efficacy of PPV against nonbacteremic pneumococcal pneumoniaProbablePossible
Clinical efficacy of PPV against pneumococcal bacteremia/meningitisUndisputedUndisputed
Clinical efficacy of PCV against nonbacteremic pneumococcal pneumoniaPresumed but not specifically studied in young adultsDemonstrated but incomplete; hence, public health benefit disputed
Clinical efficacy of PCV against pneumococcal bacteremia/meningitisPresumed but not specifically studied in young adultsUndisputed but limited serotype coverage