Background: Healthcare workers' influenza rates are unknown but may be similar to those of the general public. Healthcare workers may transmit influenza to patients.
Objectives: To identify all randomised controlled trials (RCTs) and non-RCTs assessing the effects of vaccinating healthcare workers on the incidence of laboratory-proven influenza, pneumonia, death from pneumonia and admission to hospital for respiratory illness in those aged 60 years or older resident in long-term care institutions (LTCIs).
Search methods: We searched CENTRAL 2013, Issue 2, MEDLINE (1966 to March week 3, 2013), EMBASE (1974 to March 2013), Biological Abstracts (1969 to March 2013), Science Citation Index-Expanded (1974 to March 2013) and Web of Science (2006 to March 2013).
Selection criteria: Randomised controlled trials (RCTs) and non-RCTs of influenza vaccination of healthcare workers caring for individuals aged 60 years or older in LTCIs and the incidence of laboratory-proven influenza and its complications (lower respiratory tract infection, or hospitalisation or death due to lower respiratory tract infection) in individuals aged 60 years or older in LTCIs.
Data collection and analysis: Two authors independently extracted data and assessed risk of bias.
Main results: We identified four cluster-RCTs (C-RCTs) (n = 7558) and one cohort study (n = 12,742) of influenza vaccination for HCWs caring for individuals ≥ 60 years in LTCFs. Three RCTs (5896 participants) provided outcome data that met our criteria. These three studies were comparable in study populations, intervention and outcome measures. The studies did not report adverse events. The principal sources of bias in the studies related to attrition and blinding. The pooled risk difference (RD) from the three cluster-RCTs for laboratory-proven influenza was 0 (95% confidence interval (CI) -0.03 to 0.03) and for hospitalisation was RD 0 (95% CI -0.02 to 0.02). The estimated risk of death due to lower respiratory tract infection was also imprecise (RD -0.02, 95% CI -0.06 to 0.02) in individuals aged 60 years or older in LTCIs. Adjusted analyses which took into account the cluster design did not differ substantively from the pooled analysis with unadjusted data.
Authors' conclusions: The results for specific outcomes: laboratory-proven influenza or its complications (lower respiratory tract infection, or hospitalisation or death due to lower respiratory tract illness) did not identify a benefit of healthcare worker vaccination on these key outcomes. This review did not find information on co-interventions with healthcare worker vaccination: hand-washing, face masks, early detection of laboratory-proven influenza, quarantine, avoiding admissions, antivirals and asking healthcare workers with influenza or influenza-like-illness (ILI) not to work. This review does not provide reasonable evidence to support the vaccination of healthcare workers to prevent influenza in those aged 60 years or older resident in LTCIs. High-quality RCTs are required to avoid the risks of bias in methodology and conduct identified by this review and to test further these interventions in combination.