For search strategy and selection criteria see Methods.
ReviewInfluenza vaccination for health-care workers who work with elderly people in institutions: a systematic review
Introduction
Elderly people (aged 60 years or older) in institutions such as long-stay hospital wards and nursing homes are at risk of multiple sources of infection, especially if afflicted by multiple pathologies.1, 2, 3, 4
Health-care workers—eg, nurses, doctors, other health professionals, cleaners, and porters—have substantial rates of clinical and subclinical influenza during influenza seasons.5, 6 These people often continue to work when infected with influenza,7 and can transmit influenza to patients.8, 9
The US Centers for Disease Control (CDC) Advisory Committee on Immunization Practices recommends vaccination of all health-care workers,10, 11 relying on the idea that achieving increased vaccination rates for people living in closed settings (eg, nursing homes and other chronic-care facilities) and for staff can reduce the risk of outbreaks by inducing herd immunity.
The Cochrane review of the effects of influenza vaccines in elderly people12, 13 identified five randomised controlled trials, 49 cohort studies, and ten case-control studies. The reviews showed that in homes for elderly people with good vaccine match and high viral circulation the effectiveness of vaccines against influenza-like illness was 23% (95% CI 6–36%), but was non-significant against laboratory-proven influenza (relative risk 1·04, 0·43–2·51). Well-matched vaccines prevented pneumonia (vaccine effectiveness 46%, 30–58%), hospital admission for influenza or pneumonia (effectiveness 45%, 16–64%), and deaths from influenza or pneumonia (effectiveness 42%, 17–59%), and reduced all-cause mortality (effectiveness 60%, 23–79%).
The Cochrane review of healthy adults younger than 60 years14 found that for serologically proven cases of influenza, in two trials aerosol live vaccines reduced the number of cases on average by 79% (44–92%), and in nine trials inactivated parenteral vaccines reduced cases on average by 67% (51–78%). 28 studies showed that the vaccines matched the circulating strain, and for the placebo-controlled trials parenteral inactivated vaccines were associated with a 33% (20–44%) reduction in clinical cases of influenza (influenza-like illness), and when both the vaccine matched the circulating strain and cases were serologically confirmed vaccine efficacy was 75% (62–84%).
These two Cochrane reviews show that influenza vaccine reduces the complications of influenza and mortality from complications in institutionalised elderly people, and also that healthy individuals younger than 60 years (which includes most health-care workers) have fewer cases of serologically proven influenza, especially when the vaccine matches the circulating strain.
There are two non-Cochrane systematic reviews of the effects of influenza vaccines in elderly people, but they identified fewer studies than the recent Cochrane reviews by Rivetti and colleagues12 and Jefferson and co-workers.13 In 1995, Gross and colleagues15 identified 20 cohort studies of those aged 65 years and older. In 2002, Vu and colleagues16 identified 49 studies of those 65 years and older living in the community who received inactivated influenza vaccine, retained 15 for meta-analysis, and concluded that influenza-like illness was reduced by 35% (95% CI 19–47%), admission for pneumonia and influenza by 33% (27–38%), mortality after admission for pneumonia and influenza by 47% (25–62%), and mortality from all causes by 50% (45–56%).
We aimed to investigate whether vaccination of health-care workers against influenza provides a synergistic benefit in reducing clinical cases of influenza, cases of serologically proven influenza, pneumonia, hospital admissions, and mortality in institutionalised elderly people, and whether the benefits are greater when there is a good match with the circulating strain.
Section snippets
Search strategy
We searched for single studies and systematic reviews of comparative randomised and non-randomised studies reporting the effects on viral circulation in closed institutions of any type of influenza vaccines in any schedule given to healthcare workers caring for elderly residents of long-term-care facilities aged 60 years or older in the Cochrane Central Register of Controlled Trials (CENTRAL), the Cochrane Database of Systematic Reviews, and the NHS Database of Abstracts of Reviews of
Results
We identified 312 reports retrieved for detailed assessment in the review on the effects of influenza vaccines in elderly people12, 13 and from searches by the librarian of the Cochrane Acute Respiratory Infectious Group. From those, we identified four studies possibly meeting our inclusion criteria: two cluster randomised controlled trials24, 25 and two cohort studies,21, 26 and of these we included three (panel).24, 25, 26
Undertaking randomised controlled trials of influenza vaccination in
Discussion
Although the results of individual studies in our review show a reduction in influenza-like illness, deaths from pneumonia, and deaths from all causes, there was no effect on serologically proven influenza or lower respiratory tract infection, and because of the small number of observations and the risk of bias in the designs of the studies we cannot conclude with certainty that there is a synergistic benefit from vaccinating health-care workers.
Population studies provide an estimate of the
Search strategy and selection criteria
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