Influenza vaccination for healthcare workers who work with the elderly
Abstract
This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:
To identify:
(1) Randomised controlled trials (RCTs) in which patients aged 60 years and older in institutions and health care workers were vaccinated and assess whether vaccinating health care workers is effective in preventing influenza in institutionalised patients aged 60 years and older and HCWs; and
(2) RCTs of vaccinating HCWs and assess whether vaccination reduces:
(a) the incidence of influenza in HCWs; and
(b) days of absence from work.
Background
Influenza vaccination rates in elderly institutionalised patients and in healthcare workers (HCWs) and other workers who have regular contact with elderly in‐patients vary widely by institution and country.
Healthcare workers, such as nurses, doctors, other health professionals, cleaners and porters, have substantial rates of clinical and subclinical influenza during influenza seasons (as defined by sentinel general practitioners in the community or national statistics offices) (Elder 1966; Ruel 2002).
For healthy adults younger than 65 years, influenza vaccination is 70% to 90% effective in preventing infection (CDC 2003). Those who are vaccinated have 43% fewer days of sick leave and 44% fewer visits to physician's offices for upper respiratory tract infections than those who received placebo (Nichol 1995). However, only 36% of HCWs in the US have been vaccinated (CDC 2003) and nurses and doctors tend to have lower influenza vaccination rates than other HCWs.
Some institutions have found increases in HCW influenza rates after staff vaccination campaigns (Harbarth 1998; Saxén 1999). HCWs often continue to work when infected with the influenza virus (Weingarten 1989). Weingarten also found that staff who planed to be vaccinated had been vaccinated in previous years and believed that they were susceptible to influenza and that vaccine was protective to patients and themselves. Staff who did not plan to be vaccinated had not been vaccinated in previous years and said they did not believe they were susceptible, the vaccine was not effective and they were fearful of side‐effects such as Guillain‐Barré syndrome (Begue 1998; Beguin 1998; Heimberger 1995). Influenza rates and complications such as pneumonia, congestive heart failure and death can vary greatly between institutions during epidemics.
The National Foundation for Infectious Diseases (NFID 2004) recommends making vaccination of HCWs convenient, removing cost barriers, educating HCWs, and states that top management must become strong advocates for the vaccine.
Russell (Russell 2003a; Russell 2003b) has noted that vaccination programmes should prioritise those with direct contact with patients at high risk for influenza‐related complications, and target all HCWs including temporary and contract staff, paying particular attention to staff turnover and those who refused vaccination in previous years.
There are Cochrane reviews assessing the effects of influenza vaccines in people affected by chronic obstructive pulmonary disease (Poole 2000), asthma (Cates 2003), and cystic fibrosis (Tan 2000). No Cochrane review is available which assesses the separate and combined effects of vaccinating against influenza the institutionalised elderly and the HCWs who work in the institutions where the institutionalised elderly reside, and which patients and HCWs benefit from vaccination. Presently there are only two non‐Cochrane systematic reviews of the effects of influenza vaccines in the elderly. The conclusions of Gross 1995 may be affected by the lack of inclusion of recent evidence. Vu 2002 shows several methodological weaknesses which are likely to undermine the authors' conclusion (for example the exclusion of studies with denominators smaller than 30 and quantitative pooling of studies of different design).
Objectives
To identify:
(1) Randomised controlled trials (RCTs) in which patients aged 60 years and older in institutions and health care workers were vaccinated and assess whether vaccinating health care workers is effective in preventing influenza in institutionalised patients aged 60 years and older and HCWs; and
(2) RCTs of vaccinating HCWs and assess whether vaccination reduces:
(a) the incidence of influenza in HCWs; and
(b) days of absence from work.
Methods
Criteria for considering studies for this review
Types of studies
RCTs with institutionalised patients aged 60 years and older and HCWs. Non‐randomised and quasi‐randomised evidence will be analysed separately from randomised controlled trial evidence. Quality assessment of non‐randomised studies will be made in relation to the presence of potential confounders, which could make interpretation of the results difficult. The quality of case control and cohort studies (prospective and retrospective) will be evaluated using the appropriate Newcastle‐Ottawa Scales. Because of the lack of empirical evidence on the impact of methodological quality on the results of non‐randomised studies, we will use this evaluation only at the analysis stage as a means of interpreting the results. We will perform a set of sensitivity analyses for this set of studies.
Types of participants
The elderly aged 60 years or older in institutions such as nursing homes, long‐term care institutions and acute hospitals; and HCWs such as nurses, doctors, nursing and medical students, other health professionals, cleaners, porters, other workers, as well as family members and volunteers who have regular contact with the elderly in‐patients.
Types of interventions
Vaccination of patients, or staff, or both, with any influenza vaccine (including experimental vaccines) given independently, in any dose, preparation, or time schedule, compared with placebo or with no intervention. We will include both injected trivalent vaccines and live intranasal influenza vaccines and separately analyse their effects before deciding whether they can be analysed together. We will ascertain the quality of the match between the vaccine and the strains circulating during the time period of interest. We will ascertain whether antivirals were used during the time period of interest, which antivirals, doses, and duration, when the antiviral regimen began in relation to symptoms in individual residents or an outbreak in the institution, and the percentages of elderly residents, or HCWs, or both who received them.
Types of outcome measures
Outcomes for patients
Primary outcome measures for treatment efficacy and effectiveness:
(1) Cases of influenza‐like illness (ILI): the Centers for Disease Control and Prevention (CDC 2003) defines typical influenza symptoms as "an abrupt onset of fever, chills, muscle aches, headache, anorexia, dizziness and a sense of fatigue. Cough, sore throat and runny nose are also typical symptoms." We will note the specific definitions in individual studies if they differ from this.
(2) Cases of influenza: cases defined from a list of likely respiratory and systemic symptoms and signs with laboratory confirmation (by means of viral isolation and/or serological supporting evidence) of infection with influenza viruses A and/or B.
(3) Cases of ILI or influenza admitted to hospital.
(4) Deaths (total).
(5) Deaths due to ILI, influenza and their complications.
Outcomes for HCWs
(1) Cases of influenza‐like illness (ILI): cases defined from a list of likely respiratory and systemic symptoms and signs.
(2) Cases of influenza: cases defined from a list of likely respiratory and systemic symptoms and signs with laboratory confirmation (by means of viral isolation and/or serological supporting evidence) of infection with influenza viruses A and/or B.
(3) Days of absenteeism from work.
Search methods for identification of studies
We will search the following electronic databases for reports of single studies and systematic reviews: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library latest issue), the Cochrane Database of Systematic Reviews (The Cochrane Library latest issue) and the NHS Database of Abstracts of Reviews of Effectiveness (DARE) (The Cochrane Library latest issue); MEDLINE (OVID, January 1966 to present); EMBASE (Dialog 1974 to 1979; SilverPlatter 1980 to present), Biological Abstracts (SilverPlatter 1969 to present) and Science Citation Index‐Expanded (Web of Science 1974 to present).
MEDLINE will be searched using the following search terms in combination with stages I, II and III of the highly sensitive search strategy defined by the Cochrane Collaboration and detailed in Appendix 5b of the Cochrane Reviewers' Handbook (Edition 4.2):
((exp Influenza/ OR influenza) AND (exp Vaccines/ OR exp Vaccination/ OR immuniz$ OR immunis$ OR vaccin$)) OR (exp Influenza Vaccine/ OR (influenz$ adj (vaccin$ or immune$)) AND (exp Health Personnel/ OR (health personnel OR healthcare personnel OR health care personnel) OR (health worker$ OR healthcare worker$ OR health care worker$) OR (healthcare provider$ OR health care provider) OR (health practitioner$ or healthcare practitioner$ or health care practitioner$) OR health employee$ OR medical staff OR (doctor$ or physician$) OR (allied health adj (staff or personnel)) OR paramedic$ OR nursing staff OR nurses$ OR nursing auxiliary OR hospital personnel OR hospital staff OR hospital worker$ OR exp Hospitals/ OR exp Long‐Term Care/ OR exp Residential Facilities/ OR nursing home* OR (institution$ adj elderly))
We will adapt this strategy where necessary to search the other electronic databases. The searches will include any language. The search of CENTRAL will include trial reports identified in the systematic search by hand of the journal Vaccine. In order to identify additional published and unpublished studies The Science Citation Index‐Expanded will be used to identify articles that cite the relevant studies. The relevant studies will also be keyed into PubMed and the Related Articles feature used.
Bibliographies of all relevant articles obtained, any published review and proceedings from relevant conferences will be assessed for additional studies. We will also explore Internet sources: NHS National Research Register (http://www.update‐software.com/national/); the Meta‐register of Clinical Trials (http://www.controlled‐trials.com/) the digital dissertations website (http://wwwlib.umi.com/dissertations). The Vaccine Adverse Event Reporting System website will be searched (http://www.vaers.org). We will contact first or corresponding authors of relevant studies to identify further published or unpublished trials.
Data collection and analysis
Selection
Studies will be selected if they were RCTs which included individuals aged 60 years or older in institutions and HCWs and some participants who received influenza vaccination.
Validity assessment
We will ascertain the generation of the allocation schedule; concealment of treatment allocation; exclusions; and measures to implement double blinding.
Data extraction
RT will use data extraction sheets to independently assess each study for study design (see Appendix 1), study characteristics and outcomes: the period the study was conducted; funding source; country of study; were data presented by age group/occupation/health status; description of methods; participants; interventions/exposure; outcomes (effectiveness, safety); methodological quality assessment (allocation concealment; exclusions, blinding); description and definitions of interventions and outcomes; vaccine identifiers; and whether the investigators needed to be contacted before the authors could reach agreement. TOJ will independently verify the data.
Assessment of methodological quality
We will independently assess the methodological quality of the included studies using criteria on bias from the Cochrane Reviewers' Handbook and results will be introduced into the sensitivity analysis.
We will use chi‐square to test for heterogeneity, and if we retrieve more than ten RCTs we will examine the effect of the proportion of HCWs vaccinated in different institutions on the outcome measures.
Non‐randomised and quasi‐randomised evidence will be analysed separately from randomised controlled trial evidence (see Appendix 2). The study results will be described individually in the Results section.
Studies will be classified according to the following criteria:
Randomisation
A = individual participants allocated to vaccine or control group.
B = groups of participants allocated to vaccine or control group.
Generation of the allocation sequence
A = adequate, for example, table of random numbers or computer‐generated random numbers.
B = inadequate, for example, alternation, date of birth, day of the week, or case record number.
C = not described.
Allocation concealment
A = adequate, for example, numbered or coded identical containers administered sequentially, on‐site computer system that can only be accessed after entering the characteristics of an enrolled participant, or serially numbered, opaque, sealed envelopes.
B = possibly adequate, for example, sealed envelopes that are not sequentially numbered or opaque.
C = inadequate, for example, open table of random numbers.
D = not described.
Blinding
A = adequate double blinding, for example, placebo vaccine.
B = single blind, i.e., blinded outcome assessment.
C = no blinding.
Follow up
Average duration of follow up and number of losses to follow up.
Arbitration procedure
In case of disagreement between two authors, VD will arbitrate.
Data collection
RT will extract data using a data extraction form (see Appendix 3).
Data will be checked and entered onto customised software. Data on the following will be extracted:
Methodological quality of studies;
Study design (see Appendix 1);
Description of setting;
Characteristics of participants;
Description of vaccines (content and antigenic match);
Description of outcomes;
Publication status;
Date of study;
Location of study.
Data analysis
Aggregation of data will be dependent on the sensitivity and homogeneity of definitions of exposure, populations and outcomes used. Where studies are found to be homogenous, we will perform a meta‐analysis of these studies within each design category.
We will also attempt subgroup analysis on the basis of the results of quality assessment and perform sensitivity analysis accordingly. We will use the random effects model to test the effects of possible data heterogeneity on the results of the meta‐analysis.
Quasi‐randomised and non‐randomised evidence will be analysed separately from randomised controlled trial evidence. The study results will be described individually in the Results section.
