Review
Influenza vaccination for health-care workers who work with elderly people in institutions: a systematic review

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Summary

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.

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

For search strategy and selection criteria see Methods.

References (40)

  • LE Nicolle et al.

    Twelve-month surveillance of infections in institutionalized elderly men

    J Am Geriatric Soc

    (1984)
  • MM Jackson et al.

    Intensive surveillance for infections in a three-year study of nursing home patients

    Am J Epidemiol

    (1992)
  • L Fune et al.

    Infectious disease among residents of nursing homes

    Annals of Long-term Care

    (1999)
  • AG Elder et al.

    Incidence and recall of influenza in a cohort of Glasgow healthcare workers during the 1993–4 epidemic: results of serum testing and questionnaire

    BMJ

    (1996)
  • N Ruel et al.

    Outbreaks due to respiratory syncytial virus and influenzavirus A/H3N in institutionalized aged. Role of immunological status to influenza vaccine and possible implication of caregivers in the transmission

    Presse Medicale

    (2002)
  • FB Coles et al.

    An outbreak of influenza A (H3N2) in a well-immunized nursing home population

    J Am Geriat Soc

    (1992)
  • A Yassi et al.

    Morbidity, cost and role of health care worker transmission in an influenza outbreak in a tertiary care hospital

    Can J Infect Dis

    (1993)
  • CB Bridges et al.

    Prevention and control of influenza: recommendations of the Advisory Committee on Immunization Practices (ACIP)

    MMWR Recomm Rep

    (2003)
  • SA Harper et al.

    Prevention and control of influenza: recommendations of the Advisory Committee on Immunization Practices (ACIP)

    MMWR Recomm Rep

    (2004)
  • D Rivetti et al.

    Vaccines for preventing influenza in the elderly

    Cochrane Database Syst Rev

    (2005)
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