Community management of lower respiratory tract infection in adults
Section 9: Immunisation

The complications of influenza infection include both viral and bacterial pneumonia and are associated with a high rate of morbidity and mortality in vulnerable groups, often overwhelming hospital services during the winter months. The most common cause of bacterial pneumonia is the pneumococcus, which causes the majority of community acquired pneumonia. Pneumococcal bacteraemia is a serious invasive disease with a high mortality that is frequently associated with pneumococcal pneumonia. Therefore, both Streptococcus pneumoniae and the influenza A and B viruses are important pathogens commonly affecting the 65 years and over age group and others with high risk conditions.

9.1 Influenza vaccination

Influenza vaccine is prepared each year using viruses similar to those considered most likely to be circulating in the forthcoming winter. The UK Departments of Health115 recommend that the influenza vaccine is given to all people aged 65 years or older and to people of any age

Studies of the safety of influenza vaccine have concluded that the incidence of systemic reactions is low (<5%) and that systemic side effects are equally common in the vaccine and placebo groups.116,117,118 Evidence level 1+

Several large, well designed case-control studies have shown that influenza vaccination reduces admissions for pneumonia and influenza in the elderly and/or reduces mortality from respiratory and all causes.116,119,120,121,122,123,124,125 Vaccination was also shown to be associated with fewer hospitalisations for pneumonia and influenza and fewer outpatient visits for all respiratory conditions in the elderly with chronic lung disease.126 Evidence level 2++

A meta-analysis of 20 cohort studies in patients over 65 years, described pooled estimates of vaccine efficacy of 56% for preventing respiratory illness, 53% for preventing pneumonia, 50% for preventing hospitalisation and 68% for preventing death.127 Evidence level 2++

While studies in "high risk" groups (including those with chronic lung, heart, renal and liver disease, diabetes mellitus, immunosuppression due to disease or treatment and those aged over 65 years) have shown benefit from influenza vaccination, it remains less clear whether "low risk" occupational groups (including all health and social care workers who have direct patient contact or contact with vulnerable clients) should be offered immunisation. One study has reported that influenza vaccination of health-care workers is associated with a substantial decrease in mortality among elderly people in long-term care. However, virological surveillance showed no associated decrease in non-fatal influenza infection.128

One RCT revealed that hospital employees show no significant reduction in influenza-like illness, severity of illness or sickness absenteeism.129 A more recent study, showed 25% fewer episodes of upper respiratory illness, 43% fewer days of sick leave and 44% fewer visits to physicians' offices for upper respiratory tract illness in those receiving active vaccine.130 Another RCT has shown that influenza vaccination of healthy working adults reduces the rates of influenza-like illness, lost workdays and physician visits during the year when the vaccine and circulating viruses are similar. However, during a season when the vaccine is poorly matched, vaccination does not reduce influenza-like illness, physician visits or lost workdays. During both seasons, no overall economic benefits can be demonstrated.131 Evidence level 1+


9.2 Pneumococcal vaccination

 

The current 23-valent pneumococcal polysaccharide vaccine (PPV) covers more than 95% of invasive disease serotypes in Scotland.132

Four large early RCTs confirmed the high efficacy of PPV against both pneumococcal pneumonia and invasive pneumococcal disease in immunocompetent adults who are at risk because of their occupational or social circumstances.133,134,135,136 As a result the vaccine was licensed in 1977, before large RCTs could be conducted amongst higher risk groups including the elderly, those with underlying medical conditions and those specifically immunocompromised by HIV, haematological disorders/malignancies and splenic dysfunction. The high efficacy in immunocompetent younger adults was used to under-estimate required sample sizes for the trials in higher risk groups where efficacy was bound to be lower and the actual sample sizes required even higher. As a result, the published RCTs in the elderly and those with underlying medical conditions have not consistently shown a benefit in terms of reduced pneumococcal pneumonia 137,138 although at least three have demonstrated a non-statistically significant reduced risk of pneumococcal bacteraemia.132,139,140 Other RCTs for specific high risk groups, including the severely immunocompromised and those with advanced malignancy, were inadequate in sample size and were primarily designed to assess immunogenicity and safety.141,142,143 One exception is the large study of black Ugandans with HIV which showed no benefit in this high risk group.144 Evidence level 1+,1-

Systematic reviews or meta-analyses of these small and flawed RCTs have been published.145,146,147 The verdict regarding the efficacy amongst elderly and other higher risk patients differ amongst the three publications with only one 146 concluding that the vaccine was equally efficacious for the elderly, institutionalised people or those with chronic disease. Evidence level 1-

However, there is now an extensive literature calling into question the validity of meta-analyses that group together inadequately sized and otherwise flawed studies using different outcome measures 148,149,150,151,152 and the advantages of observational studies in this situation.153,154 As a result, the most valid conclusion of the review of RCTs is that they fail to provide estimates of efficacy against pneumococcal pneumonia in the elderly, those with underlying medical conditions and the severely immunocompromised, which therefore remain unknown. It can reasonably be assumed that the efficacy of PPV in these higher risk groups is less than that estimated in the original studies, decreasing with increasing degree of immunocompromised state.

The more numerous observational studies have consistently shown a benefit. Four out of five case control studies,155,156,157,158,159 a prospective cohort study,160 and an indirect cohort study161,162,163 have all demonstrated clear protective effects with the use of the vaccine against invasive pneumococcal infection, a clear and unambiguous endpoint. In addition, the vaccine was associated with fewer hospitalisations for pneumonia, fewer deaths and direct medical care cost savings in patients with chronic lung disease.164,165 As a result, the current international consensus is that the vaccine can be considered to be 50-80% effective against invasive pneumococcal disease.166,167,168 Evidence level 2++,4

Two recent studies of cost-effectiveness, one based in America 169 and the other in five European countries 170 suggest that, based on the reduction of pneumococcal bacteraemia, the vaccine is cost-effective. Compared with preventing bacteraemic pneumococcal pneumonia alone (the bulk of invasive pneumococcal disease), the cost-effectiveness of pneumococcal vaccination increases substantially when only a small proportion of additional cases of non-bacteraemic pneumococcal pneumonia are prevented.171

Although some of the evidence is conflicting, it seems reasonable to conclude that at least in immunocompetent patients, the current vaccine is clinically highly effective for preventing pneumococcal pneumonia and associated bacteraemia. The evidence of benefit in terms of preventing invasive pneumococcal disease in the elderly and those with underlying medical conditions remains persuasive. Efficacy against pneumococcal pneumonia in these higher risk groups is unknown because it has yet to be properly studied. Nevertheless, the possibility that PPV prevents some pneumococcal pneumonia in the elderly and those with underlying medical conditions remains likely even though the efficacy is expected to be lower in these groups and even lower in immunocompromised patients.

Given the need to prevent this infection in the increasing numbers of elderly and in the face of increasing antimicrobial resistance to S. pneumoniae, it seems reasonable to specifically advocate its use in the 65+ age group, particularly given the recent reduction in the age-related indication for influenza vaccine and the evidence that the protective effects of simultaneous pneumococcal and influenza vaccination (at different sites) are additive and that their concurrent administration is safe.172 Evidence level 1++

Current UK Department of Health Joint Committee on Vaccination and Immunisation
guidelines173 recommend that PPV should not be given during acute infection and is not recommended during pregnancy. Revaccination with PPV within three years is contraindicated but revaccination after five years should be considered in those at increased risk including asplenic, hyposplenic and nephrotic patients.

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