Systematic review
Influenza vaccination of elderly and people with chronic illness
Systematic review
|Updated
This review presents the available documentation of the health effects of influenza vaccination to the elderly and people suffering from chronic illness.
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Key message
This review presents the available documentation of the health effects of influenza vaccination to the elderly and people suffering from chronic illness.
We searched for systematic reviews of the effects of influenza vaccine to the elderly and chronic ill. We updated the systematic reviews that we included, and we searched for randomized controlled trials (RCTs) of the effect of influenza vaccine to people with chronic illness. We included the following outcomes; all cause mortality, complications due to influenza (pneumonia), hospital admissions, influenza (laboratory confirmed), influenza like illness and adverse events.
We included five systematic reviews that assessed the effect of influenza vaccination to the elderly, to people with chronic obstructive lung disease, asthma, bronchiectasis, and cystic fibrosis. We included one RCT and 12 observational studies for update of the effect of influenza vaccination on elderly. We additionally included four RCTs where the effect had been measured in people with cirrhosis of the liver, multiple sclerosis, HIV- infection, and cardio vascular disease.
The evidence for influenza vaccine to elderly included more than 2,5 million people who had been included in six RCTs and 60 observational studies. Results indicate that influenza vaccine possibly reduce the risk of influenza and influenza like illness for community dwelling elderly. Influenza vaccine does possibly not influence the risk of all cause mortality or pneumonia for community dwelling elderly. Influenza vaccine possibly reduce the risk of influenza like illness for elderly living in institution, people with chronic hearth disease and people with HIV-infection. The quality of the evidence is low and very low, and results are uncertain. For the other outcomes and the other chronic diseases, evidence were either lacking or of very low quality.
The evidence regarding effect of influenza vaccine to elderly and people with chronic illness is sparse.
Summary
Background
Elderly people and people who suffer from chronic illness are encouraged to get the influenza vaccine. There have, however, been raised questions regarding the effectiveness. This review presents the available documentation of the health effects of influenza vaccination to the elderly and people suffering from chronic illness.
Methods
We searched for systematic reviews of the effects of influenza vaccine to the elderly and chronic ill. We updated the systematic reviews that we included, and we searched for randomized controlled trials (RCTs) of the effect of influenza vaccine to people with chronic illness. We included the following outcomes:
- all cause mortality
- complications due to influenza (pneumonia)
- hospital admissions
- influenza (laboratory confirmed)
- influenza like illness
- adverse events
We analysed the results from RCTs and observational studies separately for each of the outcomes. We have reported all the results but have based our conclusions on the studies representing the highest available quality.
Results
The literature search identified 826 references for systematic reviews; we included five systematic reviews that assessed the effect of influenza vaccination to
- elderly people
- people with chronic obstructive lung disease
- people with asthma
- people with bronchiectasis
- people with cystic fibrosis
The literature search for studies identified 3155 references; we included one RCT and 12 observational studies for update of the effect of influenza vaccination on elderly people. We additionally included four RCTs where the effect had been measured in people with
- cirrhosis of the liver
- multiple sclerosis
- HIV- infection
- cardio vascular disease
The evidence for influenza vaccine to elderly included more than 2,5 million people who had been included in six RCTs and 60 observational studies. The level of evidence is of low and very low quality.
There is low quality evidence that influenza vaccine may possibly reduce the risk of influenza like illness for elderly living in institution (RR 0.51 (0.12 to 0.90) 2 RCTs, 4 357 people). The quality of the other endpoints is very low.
For community dwelling elderly, there is low quality evidence that influenza vaccine may possibly reduce the risk of influenza (RR 0.39 (0.24 to 0.63) 2 RCTs, 2 473 people), and influenza like illness (RR 0.60 (0.47 to 0.78) 3 RCTs, 3 172 people). Also for elderly living in institution, there is low quality evidence that influenza vaccine possibly does not influence the risk of pneumonia (RR 0.88 (0.64 to 1.20) 2 observational studies, 18 090 people), or all cause mortality (RR 1.16 (0.34 to 4.03) 2 RCTs, 1 334 people). The quality of the other endpoints is very low.
Twice were there different conclusion between results from RCT and observational data. Both times were regarding community dwelling elderly and both times were the RCTs judged to be of low quality and the observational data of very low quality. Observational studies reported a reduction in all cause mortality when RCTs did not, and RCTs reported a reduction in laboratory confirmed influenza when observational studies did not.
There is low quality evidence that influenza vaccine may possibly reduce the risk of influenza like illness in people with chronic hearth disease (RR 0.62 (0.39 to 0.98) 2 RCTs, 959 people), and people with HIV-infection (RR 0.59 (0.36 to 0.99) 1 RCT, 102 people). Documentation for the other endpoints and other diseases is either lacking or of very low quality. The studies of influenza vaccine to people with chronic illness included chronic obstructive lung disease (180 people), asthma (353 people), chronic hearth disease (959 people), HIV-infection (102 people), liver cirrhosis (311 people), and multiple sclerosis (104 people).
Discussion
Studies including more than 2,5 million people has been conducted to assess the effect of influenza vaccine on elderly people, yet the evidence is of low and very low quality. The low quality of the evidence is explained by the fact that 97 % of the study population comes from observational studies, many of whom where there are uncertainties attached to the comparativeness of the control group, and often they do not have adjusted analysis. The RCTs also provide low quality of evidence; this is explained by the small sample size in relation to the low frequency of events.
Conclusion
Influenza vaccine may possibly reduce the risk of influenza and influenza like illness for community dwelling elderly. The risk of pneumonia and all cause mortality is possibly not affected.
Influenza vaccine may possibly reduce the risk of influenza like illness for elderly who live in an institution, people with chronic hearth disease, and people with HIV-infection. For people with chronic hearth disease, there is possibly no effect on all cause mortality.
Documentation for the other endpoints and other diseases is either lacking or of very low quality.
The evidence regarding effect of influenza vaccine to elderly and people with chronic illness is sparse.