[Show abstract][Hide abstract] ABSTRACT: Influenza vaccination of elderly individuals is recommended worldwide. Our aim was to review the evidence of efficacy and effectiveness of influenza vaccines in individuals aged 65 years or older.
We searched five electronic databases to December, 2004, in any language, for randomised (n=5), cohort (n=49), and case-control (n=10) studies, assessing efficacy against influenza (reduction in laboratory-confirmed cases) or effectiveness against influenza-like illness (reduction in symptomatic cases). We expressed vaccine efficacy or effectiveness as a proportion, using the formula VE=1-relative risk (RR) or VE*=1-odds ratio (OR). We analysed the following outcomes: influenza, influenza-like illness, hospital admissions, complications, and deaths.
In homes for elderly individuals (with good vaccine match and high viral circulation) the effectiveness of vaccines against influenza-like illness was 23% (95% CI 6-36) and non-significant against influenza (RR 1.04, 0.43-2.51). Well matched vaccines prevented pneumonia (VE 46%, 30-58) and hospital admission (VE 45%, 16-64) for and deaths from influenza or pneumonia (VE 42%, 17-59), and reduced all-cause mortality (VE 60%, 23-79). In elderly individuals living in the community, vaccines were not significantly effective against influenza (RR 0.19, 0.02-2.01), influenza-like illness (RR 1.05, 0.58-1.89), or pneumonia (RR 0.88, 0.64-1.20). Well matched vaccines prevented hospital admission for influenza and pneumonia (VE 26%, 12-38) and all-cause mortality (VE 42%, 24-55). After adjustment for confounders, vaccine performance was improved for admissions to hospital for influenza or pneumonia (VE* 27%, 21-33), respiratory diseases (VE* 22%, 15-28), and cardiac disease (VE* 24%, 18-30), and for all-cause mortality (VE* 47%, 39-54).
In long-term care facilities, where vaccination is most effective against complications, the aims of the vaccination campaign are fulfilled, at least in part. However, according to reliable evidence the usefulness of vaccines in the community is modest.
The Lancet 11/2005; 366(9492):1165-74. DOI:10.1016/S0140-6736(05)67339-4 · 45.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Influenza vaccination of elderly individuals is recommended worldwide as people aged 65 and older are at highest risk for complications, hospitalisations and deaths from influenza. The review looked at evidence from experimental and non-experimental studies carried out over 40 years of influenza vaccination. Seventy-one studies were included and were grouped first according to study design and then to setting (community or long-term care facilities). The results of the review are mostly based on non-experimental (observational) studies, which are at greater risk of bias, as not many good quality trials were available. Trivalent inactivated are the most commonly used influenza vaccines. Best effectiveness of current vaccines in preventing clinical illness and its complications was seen in long-term care facilities (for example nursing homes) where vaccines prevented about 45% of pneumonia cases, hospital admissions and influenza-related deaths. This compared to about 25% vaccine efficacy in preventing hospitalisation from influenza or respiratory illness in open community settings. The public health safety profile of the vaccines appears to be acceptable.
[Show abstract][Hide abstract] ABSTRACT: Our aim was to review the evidence of efficacy and effectiveness of influenza vaccination of health-care workers in reducing cases of influenza-like illness, influenza, complications from influenza, death from influenza, and death from all causes among the elderly people they care for in institutions. We searched 11 electronic databases in any language and identified two cluster-randomised controlled trials with moderate risk of bias and one cohort study at high risk of bias that addressed our questions. Staff vaccination had a significant effect on influenza-like illness (vaccine effectiveness [VE] 86%, 95% CI 40-97%) only when patients were vaccinated too. If patients were not vaccinated, staff immunisation had no effect. Vaccinating health-care workers did not appear efficacious against influenza (RR 0.87, 95% CI 0.46-1.63). There was no significant effect of vaccination on lower respiratory tract infections: (RR 0.70, 95% CI 0.41-1.20). Deaths from pneumonia were significantly reduced (VE 39%, 95% CI 2-62%), as were deaths from all causes (VE 40%, 95% CI 27-50%). These findings must be interpreted in the light of possible selection, performance, attrition, and detection biases.
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