Influenza vaccination for healthcare workers who care for people aged 60 or older living in long‐term care institutions New search for studies and content updated (no change to conclusions), comment added to review

Abstract

Abstract 

Background 

A systematic review found that 3% of working adults who had received influenza vaccine and 5% of those who were unvaccinated had laboratory‐proven influenza per season; in healthcare workers (HCWs) these percentages were 5% and 8% respectively. 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 (2015, Issue 9), MEDLINE (1966 to October week 3, 2015), EMBASE (1974 to October 2015) and Web of Science (2006 to October 2015), but Biological Abstracts only from 1969 to March 2013 and Science Citation Index‐Expanded from 1974 to March 2013 due to lack of institutional access in 2015.

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. Effects on dichotomous outcomes were measured as risk differences (RDs) with 95% confidence intervals (CIs). We assessed the quality of evidence with GRADE.

Main results 

We identified four cluster‐RCTs and one cohort study (n = 12,742) of influenza vaccination for HCWs caring for individuals ≥ 60 years in LTCIs. Four cluster RCTs (5896 residents) provided outcome data that addressed the objectives of our review. The studies were comparable in their study populations, intervention and outcome measures. The studies did not report adverse events. The principal sources of bias in the studies related to attrition, lack of blinding, contamination in the control groups and low rates of vaccination coverage in the intervention arms, leading us to downgrade the quality of evidence for all outcomes due to serious risk of bias.

Offering influenza vaccination to HCWs based in long term care homes may have little or no effect on the number of residents who develop laboratory‐proven influenza compared with those living in care homes where no vaccination is offered (RD 0 (95% CI ‐0.03 to 0.03), two studies with samples taken from 752 participants; low quality evidence). HCW vaccination probably leads to a reduction in lower respiratory tract infection in residents from 6% to 4% (RD ‐0.02 (95% CI ‐0.04 to 0.01), one study of 3400 people; moderate quality evidence). HCW vaccination programmes may have little or no effect on the number of residents admitted to hospital for respiratory illness (RD 0 (95% CI ‐0.02 to 0.02, one study of 1059 people; low quality evidence). We decided not to combine data on deaths from lower respiratory tract infection (two studies of 4459 people) or all cause deaths (four studies of 8468 people). The direction and size of difference in risk varied between the studies. We are uncertain as to the effect of vaccination on these outcomes due to the very low quality of evidence. Adjusted analyses, which took into account the cluster design, did not differ substantively from the pooled analysis with unadjusted data.

Authors' conclusions 

Our review findings have not identified conclusive evidence of benefit of HCW vaccination programmes on specific outcomes of laboratory‐proven influenza, its complications (lower respiratory tract infection, hospitalisation or death due to lower respiratory tract illness), or all cause mortality in people over the age of 60 who live in care institutions. 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.

Author(s)

Roger E Thomas, Tom Jefferson, Toby J Lasserson

Abstract

Plain language summary 

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

Review question  
 We wanted to know if vaccinating healthcare workers against influenza reduces the risk of older individuals in long‐term care institutions (LTCIs) acquiring influenza infections from healthcare workers.

Background  
 The signs and symptoms of influenza are similar to those of many other respiratory illnesses, therefore 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.

Study characteristics  
 Our evidence is current to October 2015. Overall five studies were included in our review but we used data from three trials with 5896 residents . In one trial the average age was 77 and 71% were female, in another this was 82 years and 70% were female, and in the last this was 86 years and 77% were female. One study was supported by the Greater Glasgow Health Board Care of the Elderly Unit, one by the Wellcome Trust and for one there was no statement.

Key results and quality of the evidence  
 The method of randomisation used was at low risk in two trials and unclear in one. In all three studies allocation concealment and blinding were unclear. In two studies data could not be included from everyone who was recruited and this put their results at a high risk of bias. All three studies reported outcomes completely. However, in all three trials there was performance bias due to incomplete influenza vaccination of healthcare workers in the intervention arms. No studies reported on adverse events.

Offering influenza vaccination to healthcare workers who care for those aged 60 or over in LTCIs may have little or no effect on laboratory‐proven influenza (low quality evidence). HCW vaccination programmes probably have a small effect on lower respiratory tract infection (moderate quality evidence), but they may have little or no effect on admission to hospital (low quality evidence). It is unclear what effect vaccination programmes have on death due to lower respiratory tract illness (very low quality evidence) or all cause deaths (very low quality evidence).

This review did not find information on other interventions used in conjunction with vaccination of healthcare workers (for example, hand‐washing, face masks, early detection of laboratory‐proven influenza, quarantine, avoiding new admissions, prompt antiviral use, asking healthcare workers with an influenza‐like illness not to work). High quality randomised controlled trials testing combinations of these interventions are needed.

Author(s)

Roger E Thomas, Tom Jefferson, Toby J Lasserson

Reviewer's Conclusions

Authors' conclusions 

Implications for practice 

The four cluster‐randomised controlled trials (RCTs) contributing outcome data to our review are at high risk of bias and pooled data have not shown convincing evidence of benefit on the outcomes of direct interest, namely laboratory‐proven influenza (low quality evidence), lower respiratory tract infections (moderate quality evidence), admissions to hospital (low quality evidence), and deaths from lower respiratory tract illness or from all causes (very low quality evidence). Where meta‐analysis was possible the 95% confidence interval (CI) in each case has not excluded little or no effect of vaccination programmes. We conclude that there is an absence of high quality evidence that vaccinating healthcare workers against influenza protects people aged 60 years or older in their care on influenza‐specific outcomes. There is little evidence to justify medical care and public health practitioners mandating influenza vaccination for healthcare workers who care for the elderly in long‐term care institutions (LTCIs).

Implications for research 

There are currently only three cluster‐RCTS that provide outcome data that meet our criteria to evaluate the impact on residents aged 60 years or older of vaccinating their healthcare workers against influenza. All of these studies are at high risk of bias. RCTs are needed with minimal risk of bias from sequence generation, failure to conceal allocation, and performance, attrition and detection bias and these should be adequately powered for the key outcomes of laboratory‐proven influenza, hospitalisation for pneumonia and death from pneumonia. They should carefully define and measure outcomes including laboratory‐proven influenza, lower respiratory tract infection, cause of hospitalisation and deaths from pneumonia. They should carefully consider the degree to which they must, to adequately assess outcomes, obtain proof of diagnosis for all participants by laboratory testing all participants with appropriate symptoms for influenza and all other likely viruses, performing blood cultures, white blood cell counts and other laboratory investigations and chest X‐rays if pneumonia is suspected, and following the course of all hospitalised patients by scrutinising individual records so that they can definitively assess all outcomes and co‐morbidities. A particular issue in the analysis of data from studies with a cluster design is the provision and use of an intra‐cluster correlation coefficient (ICC). It is a major limitation with the analysis of data in our review that we have not had available a reliable estimate of this quantity for each of the outcomes of interest.

The area of interest is those aged 60 years or older in LTCIs. Therefore, if the existing LTCIs' organisational structure is to be used to implement the interventions, these will need to be given to clusters of residents aged 60 years or older and healthcare workers, which will make blinding difficult. An important ethical issue is informed consent by those aged 60 years or older and healthcare workers. It is not ethical to blind participants or healthcare workers but the researchers, data assessors and statisticians could all be blinded.

The elderly are much keener to be vaccinated than healthcare workers and there is extensive literature about the group of healthcare workers who say they do not feel vulnerable to influenza, do not believe the vaccine is effective and are afraid of side effects, and some of these do not perceive risk for their patients. Persistence of these beliefs may limit uptake by healthcare workers and make it difficult to test conclusively the effect of very high levels of healthcare worker influenza vaccination.

A large publicly funded trial is needed to test combinations of interventions to reduce influenza and mortality from influenza in those aged 60 years or older in LTCIs with thorough delivery of each intervention: vaccinating residents and healthcare workers, hand‐washing, face masks, early detection of laboratory‐proven influenza in individuals with influenza‐like illness by using nasal swabs, quarantine of floors and entire LTCIs during outbreaks, avoiding new admissions, prompt use of antivirals and asking healthcare workers with an influenza‐like illness not to present for work.

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