Influenza vaccination for healthcare workers who care for people aged 60 or older living in long-term care institutions

Older individuals in long-term care institutions (LTCIs) at risk of influenza may be infected by their healthcare workers. There are no accurate data on rates of laboratory-proven influenza in healthcare workers. Vaccinating healthcare workers against influenza may reduce infections acquired from this source. Because the signs and symptoms of influenza are similar to those of many other respiratory illnesses, it is important in studies testing the effects of influenza vaccination to prove by laboratory tests which are highly accurate whether residents in LTCIs actually have influenza or another respiratory illness.

Three randomised controlled trials (RCTs) (5896 participants) provided outcome data meeting our criteria. For risk of bias: randomisation was at low risk in two trials and unclear in one; allocation concealment and blinding in all three trials was unclear; incomplete outcome data in one trial was at low risk and in two at high risk; selective reporting all three trials was at low risk; performance bias (incomplete influenza vaccination of healthcare workers in the intervention arms) in all three trials was at high risk. No studies reported on adverse events. Vaccinating healthcare workers who care for those aged 60 or over in LTCIs showed no effect on laboratory-proven influenza or complications (lower respiratory tract infection, hospitalisation or death due to lower respiratory tract illness) in those aged 60 or over resident in LTCIs.

This review did not find information on other interventions used in conjunction with vaccinating healthcare workers (hand-washing, face masks, early detection of laboratory-proven influenza, quarantine, avoiding new admissions, prompt use of antivirals and asking healthcare workers with an influenza-like illness not to work.

There is no evidence that only vaccinating healthcare workers prevents laboratory-proven influenza or its complications (lower respiratory tract infection, hospitalisation or death due to lower respiratory tract infection) in individuals aged 60 or over in LTCIs and thus no evidence to mandate compulsory vaccination of healthcare workers. Other interventions, such as hand-washing, masks, early detection of influenza with nasal swabs, antivirals, quarantine, restricting visitors and asking healthcare workers with an influenza-like illness not to attend work, might protect individuals over 60 in LTCIs. High-quality randomised controlled trials testing combinations of these interventions are needed.

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.

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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 strategy: 

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.