Pneumococcal disease in the elderly: what is preventing vaccine efficacy?
The effective prevention of Streptococcus pneumoniae infection has a renewed priority in an era in which the emergence of antibacterial-resistant strains has the potential to further compromise efforts to reduce early mortality from invasive pneumococcal infection. Although the 23-valent pneumococcal polysaccharide (PPS) vaccine was approved in the US to prevent respiratory and invasive infection in the elderly and other high-risk populations, the protective efficacy of this vaccine for the growing population of adults aged >65 years remains controversial. The apparent effectiveness of pneumococcal immunisation in clinical studies of elderly adults has varied depending upon whether a reduction in pneumococcal colonisation, pneumonia, bacteraemia or death was used as an outcome. Clinical studies of vaccine efficacy to date suggest that the current pneumococcal vaccine is 56 to 81% effective at preventing invasive pneumococcal infection, and may have additive benefit to influenza vaccine in preventing community-acquired pneumonia, particularly in elderly adults with an increased risk of serious pneumonia requiring hospitalisation. Possible reasons for incomplete protection from pneumococcal infection after immunisation include infection with non-vaccine serotypes, inadequate or ineffective antibody responses, waning of antibody responses, or compromised nonhumoral host defences. Further studies are needed to determine whether: (i) elderly adults who respond poorly to the 23-valent pneumococcal vaccine can be identified prior to immunisation and targeted for study with improved pneumococcal vaccines; (ii) specific nutrient deficiencies can be identified and corrected to improve the immune responsiveness of elderly adults to the PPS vaccine; (iii) newer protein-conjugate or DNA pneumococcal vaccines may be more uniformly immunogenic for elderly adults; and (iv) whether smoking cessation reduces the risk of invasive pneumococcal infection in elderly adults.
Rubins
J B
JB
Pulmonary Diseases, Veterans Affairs Medical Center and Department of Medicine, University of Minnesota School of Medicine, Minneapolis 55417, USA. rubin004@tc.umn.edu
Janoff
E N
EN
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D002986:Clinical Trials as Topic; D006801:Humans; D011008:Pneumococcal Infections / Q000276:immunology / Q000517:prevention & control*; D022242:Pneumococcal Vaccines / Q000008:administration & dosage* / Q000276:immunology; D013296:Streptococcus pneumoniae / Q000276:immunology; D016896:Treatment Outcome
D022242:Pneumococcal Vaccines