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

  1. Roger E Thomas1,*,
  2. Tom Jefferson2,
  3. Toby J Lasserson3

Editorial Group: Cochrane Acute Respiratory Infections Group

Published Online: 22 JUL 2013

Assessed as up-to-date: 31 MAR 2013

DOI: 10.1002/14651858.CD005187.pub4


How to Cite

Thomas RE, Jefferson T, Lasserson TJ. Influenza vaccination for healthcare workers who care for people aged 60 or older living in long-term care institutions. Cochrane Database of Systematic Reviews 2013, Issue 7. Art. No.: CD005187. DOI: 10.1002/14651858.CD005187.pub4.

Author Information

  1. 1

    University of Calgary, Department of Family Medicine, Faculty of Medicine, Calgary, Alberta, Canada

  2. 2

    The Cochrane Collaboration, Roma, Italy

  3. 3

    The Cochrane Collaboration, Cochrane Editorial Unit, London, UK

*Roger E Thomas, Department of Family Medicine, Faculty of Medicine, University of Calgary, UCMC, #1707-1632 14th Avenue, Calgary, Alberta, T2M 1N7, Canada. rthomas@ucalgary.ca.

Publication History

  1. Publication Status: New search for studies and content updated (conclusions changed)
  2. Published Online: 22 JUL 2013

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Characteristics of included studies [ordered by study ID]
Carman 2000

MethodsPurpose: to assess the effects of staff vaccination against influenza on resident mortality in long-term care hospitals

Design: cluster-randomised study (C-RCT) conducted in Scotland during the 1996 to 1997 influenza season. The study identified 10 long-term care geriatric hospitals in West and Central Scotland with a policy of vaccinating all patients against influenza if they had no contraindications and then only on the request of the patients or their relatives. Pairs of hospitals in each of these clusters were matched on patient enrolment and then in a Latin square design were randomised by a table of random numbers for the HCWs to be offered influenza vaccination or not

Anonymous questionnaires were sent to ward nurses on 31 March 1997 to ask if they had received influenza vaccination and these data were used to estimate vaccine acceptance for all HCWs in hospitals where influenza vaccine had not been offered to HCWs. In each hospital a random sample chosen by computer of 50% patients was selected for virological monitoring

Data from the Scottish Centre for Infection and Epidemiological Health and from GPs were used to define the start of the influenza season. Combined nasal and throat swabs were taken from patients every 2 weeks from 14 December 1996 to 14 February 1997. Opportunistic samples were also taken from patients whom the ward nurses thought had influenza. Samples were taken within 12 hours of death of any patient who died. Samples were analyzed by RT-PCR analysis

Results were summarised for the 2 groups of LTCIs. Hospitals were not well-matched for patient vaccination rates and Barthel scores (Wikipedia 2009) and post-hoc statistical adjustments could not be made because of missing data. The outcome was the empirical logic of mortality for each cluster (= natural logarithm of the odds on death)

Statistics: the power calculation was based on the previous study by Potter 1997 and the authors computed that with 1600 patients in 20 hospitals they would have ≥ 80% power to detect a decrease in mortality from 15% to 10% with alpha = 0.05 (2-tailed), allowing for the clustered design. The power calculation for virological sampling showed that 500 patients would be required to give 80% power at 5% significance (2-tailed) to detect a decrease in influenza infection from 25% to 15%

Mortality rates were compared in the 2 groups with the Mann-Whitney test. "Incomplete data for patient-level covariates meant that a full multilevel approach to the analysis was not possible without making strong, implausible and untestable assumptions about the mechanisms that led to the incomplete data. Instead, we calculated summary statistics to describe the mix of patients in each hospital and these values were included in a multiple linear-regression analysis. The response variable in these analyses was the empirical logit of each hospital's mortality rate that is, the natural logarithm of the odds on death."


ParticipantsCountry: Scotland

Setting: 20 long-term care hospitals in Glasgow

Eligible participants: 749 participants were residents of facilities in the arm in which 1217 HCWs were offered vaccination (620 accepted) and 688 in the arm in which HCWs were not offered vaccination. Day and night nurses, doctors, therapists, porters and ancillary staff (including domestic staff and ward cleaners) were offered influenza vaccination

Age: 82

Gender: 70% F


InterventionsIntervention: influenza vaccination. The type, dosage and route are not described. A good match in the study year between the prevailing strain and the vaccine strains was reported

Control: no influenza vaccination


Outcomes
  1. RT-PCR and tissue culture for influenza A or B. A random sample of 50% of patients in each hospital was selected for virological monitoring of influenza infections by nose and throat swabs every 2 weeks, which were sent for RT-PCR analysis and tissue culture. "At the times when study nurses took routine samples, they took additional opportunistic nose and throat swabs from non-randomised patients who the ward nurses thought had an influenza-like illness. The ward staff were asked to take routine nasal swabs within 12 hours of death for any patient who died."
  2. Mortality (all causes)


(N.B. clinical outcomes were not reported but were used to investigate the viral circulation in the facility)


NotesThe situation that 10 long-term care hospitals had a policy of routinely vaccinating residents for influenza vaccination and 10 did not, permitted a Latin square design RCT of offering influenza vaccination or not to HCWs within each of these clusters
Analysis was not according to intention-to-treat

Design effect: 2.6; source: intra-cluster variance of 2.3% reported in Hayward 2006a

Despite no difference in isolation of influenza viruses between clusters, the authors conclude that vaccines are protective. In addition, they fail to comment on the implausibility of the vaccines' effect on aspecific outcomes (ILI) and lack of effect on influenza


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Low risk"Hospitals were randomly allocated ... by random-numbers table."

Allocation concealment (selection bias)Unclear riskNot stated

Blinding (performance bias and detection bias)
All outcomes
Unclear riskNot stated

Incomplete outcome data (attrition bias)
All outcomes
High riskIn the 10 hospitals where HCWs were offered vaccination 749 patients were included and "a random sample of 375 patients was offered virological screening by nose/throat swab"; 258 accepted. In the 10 hospitals where HCWs were not offered vaccination 688 patients were included and a random sample of 344 were offered virological screening by nose/throat swab; 269 accepted. Note comments by authors in the Description section above on incomplete data. Polymerase chain reaction (PCR) samples were obtained from only 17% of deaths. Four samples from each patient surveyed were planned from protocol: 1798 samples were obtained from 719 patients (2.5 samples/patient)

Selective reporting (reporting bias)Low riskNo selective reporting

Other biasHigh risk
  1. Selection bias: the total number of long-term care hospitals in West and Central Scotland is not stated. In the long-term care hospitals in which HCWs were offered vaccination, residents had higher Barthel scores
  2. Performance bias: only 51% of HCWs in the arm received vaccine in the long-term care hospitals where vaccine was offered and 4.8% where it was not; 48% of patients received vaccine in the arm where HCWs were offered vaccination and 33% in the arm where HCWs were not
  3. Statistical bias: the analysis was not corrected for clustering, unlike the Potter 1997 pilot; in the long-term care hospitals where HCWs were offered vaccination, the patients had significantly higher Barthel scores and were more likely to receive influenza vaccine (no significance level stated) and due to missing data these differences could not be adjusted for other than by estimation. Statistical power may also have been a problem as the detection rate of 6.7% was lower than the estimated rate of 25% used in the power calculation

Hayward 2006

MethodsPurpose: to increase staff vaccination rates in care homes by adoption of a policy to encourage staff to be vaccinated against influenza and providing vaccination clinics

Design: C-RCT; 48 nursing homes were placed in matched pairs (by size of home, % of high dependency and mortality of residents) within 3 regions (northern, central and southern England), then the 25 homes which most closely matched were selected and randomised by a researcher, blinded to the home’s identity and characteristics, using a table of random numbers. Data from the Royal College of General Practitioners sentinel surveillance scheme were used to divide the study into periods of influenza activity and no influenza activity

Duration of study: 3 November 2003 to 28 March 2004 and 1 November 2004 to 27 March 2005

Interval between intervention and when outcome was measured: 3 November 2003 to 28 March 2004 and 1 November 2004 to 27 March 2005

Power computation: to detect reduction in all-cause mortality of residents from 15% to 10% (intra-cluster variance = 2.3%) with 90% power and alpha = 0.05% level required 20 pairs of homes each with an average of 20 residents (based on findings from pilot study)

Statistics: outcomes were analyzed using aggregate data for each cluster and "to take account of the matched clustered design we used a random-effects meta-analysis. This treated the results from each pair of homes as a separate study and provided a pooled estimate of effect weighted for the size of homes and the size of the effects and their standard errors." "When significant protection of residents was observed we calculated the number of staff vaccinations needed to prevent one event in residents (number needed to treat) as number of vaccinations given in all intervention homes divided by the average number of residents in all intervention homes multiplied by the weighted rate difference."


ParticipantsCountry: UK
Setting: private chain of nursing homes, whose policy was not to offer influenza vaccination to staff
Eligible participants: (health status): 1 intervention and 1 control home were unable to provide data so they and their matched home were excluded, leaving 44 homes for analysis; eligible staff were all staff in intervention homes (full-time: n = 844 in both 2003 to 2004 and in 2004 to 2005) and (part-time: n = 766 in 2003 to 2004 and n = 882 in 2004 to 2005)
Age: Avg 83
Gender: 71% F


InterventionsIntervention 1: Adoption of policy in intervention homes of vaccinating staff against influenza, including a lead nurse in each home was trained to promote vaccination of staff; distribute leaflets and posters and liaise to provide 3 vaccination clinics for staff in each home. Staff were sent a letter explaining the study and the potential benefits of influenza vaccination
Control: staff in control homes received a letter describing the study and the Department of Health recommendation that those with chronic illnesses should receive influenza vaccination
No attempt to influence vaccination of residents in any home


OutcomesPrimary outcome of the study: to assess effect of vaccinating staff on all-cause mortality of residents
Secondary outcomes: ILI (defined as fever 37.8°C measured orally, or an acute deterioration in physical or mental ability, plus either new onset or one or more respiratory symptoms or an acute worsening of a chronic condition involving respiratory symptoms), mortality with ILI, admission to hospital from any cause, admission to hospital with ILI and consultations with a GP for ILI
Other outcomes measured: % of staff vaccinated
Time points from the study that are considered in the review or measured or reported in the study: 3 November 2003 to 28 March 2004 and 1 November 2004 to 27 March 2005
% of staff vaccinated: by 28 March 2004 for first year of study and by 27 March 2005 for second year of study: full-time staff: intervention group 407/844 vaccinated; control group 51/859
Part-time staff: intervention group 163/766 vaccinated; control group 33/815


NotesFunding: UK Department of Health
Design effect: 2.3; source: calculation based on reported intra-cluster variance (2.3%) in the published paper
Vaccine content was not reported. No conclusions on matching can be drawn


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Low risk"A researcher blinded to the home’s identity and characteristics carried out randomisation within those pairs using random number tables."

Allocation concealment (selection bias)Low risk"A researcher blinded to the home’s identity and characteristics carried out randomisation."

Blinding (performance bias and detection bias)
All outcomes
Unclear riskNo statement

Incomplete outcome data (attrition bias)
All outcomes
High risk"No outcome data were available for the excluded homes so an intention to treat analysis was not possible."

Selective reporting (reporting bias)Unclear riskAlthough the study does not contribute data for relevant outcomes we are unable to ascertain whether influenza specific outcome data were collected and analyzed

Other biasLow riskNo other issues were identified

Lemaitre 2009

MethodsPurpose: to assess the effect of staff and resident influenza vaccination on resident all-cause mortality

Design: C-RCT. A written invitation was sent to the 376 nursing homes with 50 to 200 elderly people (out of a total 1105 nursing homes) in the Paris area and 88 responded. Of these 40 with staff influenza coverage < 40% during the 2005 to 2006 winter season were selected. Each institution was pair-matched on size, staff vaccination coverage 2005 to 2006 and Group Iso Resources (GIR) weighted average disability score (which ranges from 1 = severe disability to 6 = total autonomy). Randomisation was centrally based using a random-number generator

Statistics: it was assumed that the influenza epidemic would last 2 months, mortality would be 8% in the control arm and resident mortality would be reduced 40% after staff vaccination to 4.8% in the intervention arm. 20 pairs of nursing homes with 2000 residents in each group were required to obtain 80% power with 2-tailed hypothesis testing. Analysis was by intention-to-treat. "Odds ratios were calculated using alternating logistic regression, with one-nested log odds ratios to model the association between the responses of the same pair and the same nursing home within the pair." "In secondary analyses, multivariate estimates were adjusted for the residents' age, vaccination status, GIR disability score and Charlson comorbidity index."


ParticipantsCountry: France

Setting: 40 nursing homes near Paris

Eligible participants: 3483 patients in the 40 nursing homes

In the intervention arm there were 1592 residents at the beginning and 130 entered the homes during the study period (total = 1722); 989 staff were present at recruitment and 678 (68.6%) were vaccinated. In the control arm there were 1558 residents at the beginning and 120 entered the homes during the study period (total = 1678); there were 1015 staff at recruitment and 323 (31.8%) were vaccinated

1452 (84.3%) of patients in the intervention and 1385 (82.5%) in the control group were vaccinated during the 2005 to 2006 winter season

Age: 86

Gender: 77.% F


InterventionsIntervention:

  1. Promotional campaign with posters, leaflets and an information meeting with the study team to sensitise staff to the benefits of influenza vaccination for oneself and residents
  2. Face-to-face interviews with each member of staff present in nursing homes between 6 November and 15 December 2006
  3. The study team met all administrative staff, technicians and caregivers to invite them to participate and those who volunteered were vaccinated at the end of the interview. The vaccine was inactivated Influvac (Solvay Pharma Laboratories), with 15 µG of each of A/Wisconsin/67/2005-like (H3N2), A/New Caledonia/20/99 (H1NH1) and B/Malaysia/2506/2004


Control: routine information on influenza vaccination


OutcomesPrimary: all-cause mortality

Secondary:

  1. Influenza, measured when clusters of ILI occurred in residents, using the Quick View Influenza Test
  2. ILI ("defined as a fever of ≥ 37.8°C and onset of respiratory symptoms or worsening of chronic respiratory conditions"
  3. Proportion of staff who reported ≥ 1 day of sick leave


NotesDesign effect: 1.9; source: reported in published paper and confirmed by Magali Lemaitre

Choice of main outcome is inappropriate


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Low risk"Randomisation was centrally based using a random-number generator"

Allocation concealment (selection bias)Unclear riskNot stated

Blinding (performance bias and detection bias)
All outcomes
Unclear riskNot stated

Incomplete outcome data (attrition bias)
All outcomes
Low riskDuring primary study period. Intervention group: 1592 residents at beginning + 130 entered and 1722 analyzed; Control group: 1558 residents at the beginning, 120 entered, 1678 analyzed (no statement of deaths or separations)

Intervention group 989 staff (678 vaccinated); Control group 1015 staff (estimated vaccination rate 31.8%)

Selective reporting (reporting bias)Low riskNo selective reporting

Other biasHigh riskPerformance bias (delivery of influenza vaccine to intervention arm)

Oshitani 2000

MethodsPurpose: to assess the effect of staff and resident influenza vaccination rates on resident influenza-like illness (ILI)
Design: prospective cohort study assessing the effectiveness of influenza vaccination levels in patients of long-term nursing care facilities (LTCIs) by vaccination coverage rates of HCWs (less than 10 or more than 10 vaccinated HCWs per facility), in Niigata, Japan. Niigata Prefecture and Niigata City conducted mandatory surveys of influenza vaccine status and occurrence of ILI every 2 weeks from January to March 1999. During this period more than 20% of facilities had outbreaks and more than 10% of residents experienced ILI during an influenza A (H3N2) epidemic. All LTCIs in Niigata Prefecture provided reports. Information (assumed questionnaires) included number of residents in each institution, number of vaccinated residents and staff and weekly ILI in residents. No ILI definition is reported
An influenza outbreak was defined as 10% of more of the residents in a home reporting ILI symptoms during a week
Two types of LTCIs, special nursing homes for the elderly and geriatric health services facilities, were used. Both are for the elderly who need constant care, special nursing homes are for the elderly who have more severe conditions
Statistics: X2 and Fisher’s exact test for univariate analysis. X2 for linear trend and Mantel-Haenszel ORs for different categories of resident vaccination rates. Logistic regression for multivariate analysis of outbreak status


ParticipantsCountry: Japan
Setting: 149 LTCIs in Niigata Prefecture and Niigata City
Eligible participants: the text reports 12,784 residents in 149 facilities were included in the study with 3933 (30.8%) vaccinated and 7459 staff with 1532 (20.5%) vaccinated However, table 2 shows 8669 residents living in homes where fewer than 10 staff were vaccinated and 4073 living in homes with 10 staff vaccinated, for a total of 12,742. The totals for residents living in homes with fewer than 10 staff vaccinated is given as 8699 but the subcategories add to 8669 and for the homes where 10 staff were vaccinated the total is given as 4085 but the subcategories add to 4073
Age: not stated
Gender: not stated


InterventionsIntervention: trivalent influenza vaccine containing A/Beijing/262/95 (H1N1), A/Sydney/5/97 (H3N2) and B/Mie/1/93, which was a good match against the circulating strain. No mention of pneumococcal vaccination is made
Control: no control group


OutcomesILI (no case definition). During the period of surveying the number of ILI cases per week exceeded 10% of the residents in 34 (22.8%) of facilities


NotesChoice of outcome is inappropriate (ILI is an a non-specific outcome)

Assessment of the Oshitani study was undertaken with the Newcastle-Ottawa scale (see Appendix 7)


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Unclear risk-

Allocation concealment (selection bias)Unclear risk-

Blinding (performance bias and detection bias)
All outcomes
Unclear risk-

Incomplete outcome data (attrition bias)
All outcomes
Unclear risk-

Selective reporting (reporting bias)Unclear risk-

Other biasUnclear risk-

Potter 1997

MethodsPurpose: to assess the effect of staff and patient vaccination against influenza on resident

  1. Serologically proven influenza
  2. ILI
  3. Lower respiratory tract infection
  4. Deaths (from all causes)
  5. Deaths (from pneumonia)


Design: 6 geriatric long-stay hospitals in Glasgow in 1994 had an "opt-out" policy in which patients were routinely given influenza vaccine unless they refused it or had a major contraindication and 6 had an "opt-in" policy in which patients were given vaccine only if they or their relatives requested it following advertisement on the ward that it was available

Hospitals were stratified by policy on vaccination then randomised for their HCWs to be "routinely offered either influenza vaccination or no vaccination." Study conducted in Scotland, during the 1994 to 1995 influenza season, in the community. Follow-up period was 1 October 1994 to 31 March 1995. 12 hospitals were randomly allocated to offer vaccination of HCWs or not; facilities were grouped according to the vaccination policy. The vaccination of staff and patients was voluntary. The study thus presents data on four sub-populations:

- staff and patients not vaccinated (S0P0)
- staff not vaccinated, patients vaccinated (S0PV)
- staff and patients vaccinated (SVPV)
- staff vaccinated and patients not vaccinated (SVP0)

Statistical analysis: "Baseline characteristics, morbidity and mortality in the 4 groups of hospitals were compared using the X2 test, unpaired Student's test and Wilcoxon rank sum test as appropriate. Odds ratios and 95% CIs were calculated for the effects of staff and patient vaccination. Survival analysis was by Kaplan-Meier product limit estimates, using the Tarone Ware test for statistical significance. Cluster analysis, examining mortality rates and other outcomes by hospital site, was also done."


ParticipantsCountry: Scotland

Setting: 12 geriatric medical long-term care hospitals in Glasgow

Eligible participants: 1059 hospital residents. All 1078 HCWs (day and night nurses and nursing auxiliaries, ward cleaners, doctors, therapists and porters) in SVPV and SVP0 hospitals were offered vaccination but "voluntary workers, patients' friends and relatives and other casual or occasional ward visitors were not offered vaccine." Observed units were hospitals and not patients

654 (61%) of the 1078 agreed to participate; vaccination was contraindicated in 34 (3%) and 47 (4%) were on long-term sick leave and unavailable

The physical dependency level of patients was measured on the 20-point Barthel scale. The hospitals where patients were routinely offered vaccination (S0PV and SVPV) had lower Bartel scores (P = 0.003) than those not offered vaccination but there were no differences between hospitals where HCWs were vaccinated and those where they were not

Age: 77

Gender: 71% F


InterventionsVaccination of patients and HCWs began October 1994 ("4 weeks before the earliest likely start date of the annual influenza outbreak"). Parenteral influenza vaccine. Vaccine strains probably matched the circulating strain


Outcomes
  1. Serologically proven influenza (paired sera in 225 consenting patients in the "patients not vaccinated" arms)
  2. ILI (defined as a temperature of ≥ 37°C, "plus one of the following symptoms: new-onset cough, coryza, sore throat, malaise, headache, or muscle aches" - reported singly or within the ILI outcome) and was monitored from the end of October 1994 to the end of March 1995
  3. LRTI ("was identified by the presence of (1) pulmonary crackles, wheeze or tachypnoea plus temp ≥ 37 °C or WBC > 10 x 109/L or (2) a positive sputum culture" and was monitored from the end of October 1994 to the end of March 1995
  4. Deaths (from all causes)
  5. Deaths (from pneumonia)


All deaths and discharges and admissions to the wards were recorded

Ward staff notified the research nurse of any patient who developed clinical symptoms of upper respiratory tract viral illness, influenza or lower respiratory tract infection and the research nurse visited the patient within 24 hours to record symptoms, clinical signs and investigations on standardised forms. "Chest radiographs were not included as part of the routine assessment of suspected lower respiratory tract infection, as for many of the peripheral hospitals, it would have required an ambulance journey for the patient." "Patients with suspected viral illness who gave verbal consent had a nasopharyngeal aspirate (NPA) sample obtained within 48 hours of notification of symptoms. IFA for influenza A and B, respiratory syncytial virus (RSV), Chlamydia psittaci and adenovirus antigens" were obtained

Antibody levels to Mycoplasma pneumoniae (M. pneumoniae) were ascertained by complement fixation in consenting patients who had not received influenza vaccination


NotesStaff vaccination was incomplete and variable; results were presented by hospital group and not by vaccination status of patients. The authors concluded that vaccination of HCWs was associated with lower mortality and ILI. These benefits were not evident vaccinating patients alone

Design effect: 3.0; source: intra-cluster variance of 2.3% reported in Hayward 2006


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Unclear risk"Hospital sites were stratified by unit policy for vaccination, then randomised for their HCWs to be routinely offered either influenza vaccination and their patients unvaccinated (S0P0), staff vaccinated and patients unvaccinated (SVP0), staff unvaccinated and patients vaccinated (S0PV) and both staff and patients vaccinated (SVPV)"

(N.B. the phrase "either influenza vaccination and their patients unvaccinated (S0P0)" is an error and should read: "neither staff nor patients vaccinated (S0P0)")

Allocation concealment (selection bias)Unclear riskNot stated

Blinding (performance bias and detection bias)
All outcomes
Unclear riskNot stated

Incomplete outcome data (attrition bias)
All outcomes
High riskOnly 654 (61%) of the 1078 HCWs agreed to participate and receive influenza vaccination and 478 (88.8%) of the 538 patients in the "routine vaccination of patients" arms. Serologically proven influenza was ascertained in paired sera in only 225 consenting patients in the "patients not vaccinated" arms. The numbers of influenza or ILI infections in HCWs were not reported

Selective reporting (reporting bias)Low riskNo selective reporting

Other biasHigh risk
  1. Selection bias: the total number of long-term care hospitals in West and Central Scotland is not stated. There were inconsistencies in outcome gradients (see  Table 1). In the population under observation, Potter 1997 reported 216 cases of suspected viral illness, 64 cases of ILI, 55 cases of pneumonia, 72 deaths from pneumonia and 148 deaths from all causes; in the sub-population of both vaccinated staff and patients, Potter 1997 reported 24 cases of suspected viral illness, 2 cases of ILI, 7 cases of pneumonia, 10 deaths from pneumonia and 25 deaths from all causes. As these gradients are not plausible, the effect on all-cause mortality is likely to reflect a selection bias rather than a real effect of vaccination
  2. Performance bias: 67% of staff in active arm 1 and 43% in active arm 2 were vaccinated
  3. There is no description of the vaccines administered, vaccine matching or background influenza epidemiology

 
Characteristics of excluded studies [ordered by study ID]

StudyReason for exclusion

Bellei 2007Surveillance study of influenza and rhinovirus infections among HCWs; no vaccination data; no data for elderly people

Bertin 2007Intranet assessment of HCW vaccination status; no vaccination or outcome data for elderly people

Carusone 2007Study of pneumonia and lower respiratory infections in nursing home residents as predictors of hospitalisation and mortality; based on previous RCT; influenza vaccination status of patients; no HCW vaccination data

Chicaíza-Becerra 2008Economic evaluation of influenza vaccination of HCWs; no vaccination or outcome data for elderly people

Chittaro 2009Influenza vaccination campaign for HCWs; no data on elderly people

del Villar-Belzunce 2007Programme to increase influenza vaccination among HCWs; no vaccination or outcome data for elderly people

Doratotaj 2008Programme to increase influenza vaccination among HCWs; no vaccination or outcome data for elderly people

Hood 2009Programme to increase influenza vaccination among HCWs; no vaccination or outcome data for elderly people

Isaacs 1997Data were not presented by HCW vaccine coverage; only 21% of staff were vaccinated; amantadine was a confounder as it was given to patients and not staff; a flow sheet of admissions and discharges was not presented

Isahak 2007Programme to increase influenza vaccination among elderly people in long-term care homes; no vaccination data for HCWs

Kheok 2008Programme to increase influenza vaccination among HCWs; no vaccination or outcome data for elderly people

Kimura 2007Programme to increase influenza vaccination among HCWs; no vaccination or outcome data for elderly people

Landi 2006Prospective observational study of influenza vaccination in elderly people; no HCW data

Lee 2008Programme to increase influenza vaccination among HCWs; no vaccination or outcome data for elderly people

Looijmans-van den AkkerSurvey of effect of national policy on influenza vaccination among HCWs; no vaccination or outcome data for elderly people

Mangtani 2004Historical cohort study of individuals older than 64 years in the UK General Practice Research Database 1989 to 1999 in England and Wales. No intervention for HCWs

Munford 2008Campaign to increase influenza vaccination among elderly people and HCWs; no outcome data for elderly people

Sato 2005Study of antibody levels in elderly people and HCWs in response to influenza vaccination

Shugarman 2006Retrospective cross-sectional study of 344 nursing homes (310 replied) from one chain in the US, with reports of staff and resident vaccination rates and whether the home had an ILI cluster (≥ 3 residents with ILI within 72 hours)

Yang 2007Programme to increase influenza vaccination among HCWs; no vaccination or outcome data for elderly people

Yassi 1993Data were not presented by HCW vaccine coverage. Vaccine and amantadine were used to control outbreak: amantadine acts as confounder

Zimmerman 2009Programme to increase influenza vaccination among HCWs; no vaccination or outcome data for elderly people

 
Comparison 1. HCWs offered vaccination versus HCWs offered no vaccination: experimental design; data for periods of high influenza activity (Carman and Potter 152; Lemaitre 118 days)

Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size

 1 Influenza2752Risk Difference (M-H, Random, 95% CI)-0.00 [-0.03, 0.03]

    1.1 Unvaccinated patients
1225Risk Difference (M-H, Random, 95% CI)0.01 [-0.03, 0.05]

    1.2 Vaccinated and unvaccinated patients
1527Risk Difference (M-H, Random, 95% CI)-0.01 [-0.05, 0.03]

 2 Lower respiratory tract infection11059Risk Difference (M-H, Random, 95% CI)-0.02 [-0.04, 0.01]

    2.1 Vaccinated patients
1538Risk Difference (M-H, Random, 95% CI)-0.02 [-0.05, 0.01]

    2.2 Unvaccinated patients
1521Risk Difference (M-H, Random, 95% CI)-0.02 [-0.06, 0.03]

 3 Admission to hospital for respiratory illness13400Risk Difference (M-H, Random, 95% CI)0.00 [-0.02, 0.02]

    3.1 Vaccinated and unvaccinated patients
13400Risk Difference (M-H, Random, 95% CI)0.00 [-0.02, 0.02]

 4 Deaths from influenza or its complications24459Risk Difference (M-H, Random, 95% CI)-0.02 [-0.06, 0.02]

    4.1 Vaccinated patients
1538Risk Difference (M-H, Random, 95% CI)-0.03 [-0.07, 0.01]

    4.2 Unvaccinated patients
1521Risk Difference (M-H, Random, 95% CI)-0.03 [-0.07, 0.01]

    4.3 Vaccinated and unvaccinated patients
13400Risk Difference (M-H, Random, 95% CI)0.00 [-0.00, 0.01]

 
Comparison 2. HCWs offered vaccination versus HCWs offered no vaccination: experimental design; data for periods of high influenza activity (Carman and Potter 152; Lemaitre 118 days)

Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size

 1 Influenza2493Risk Difference (M-H, Random, 95% CI)0.00 [-0.03, 0.03]

    1.1 Unvaccinated patients
1160Risk Difference (M-H, Random, 95% CI)0.01 [-0.03, 0.05]

    1.2 Vaccinated and unvaccinated patients
1333Risk Difference (M-H, Random, 95% CI)-0.01 [-0.06, 0.04]

 2 Pneumonia1351Risk Difference (M-H, Random, 95% CI)-0.02 [-0.06, 0.03]

    2.1 Vaccinated patients
1178Risk Difference (M-H, Random, 95% CI)-0.02 [-0.08, 0.03]

    2.2 Unvaccinated patients
1173Risk Difference (M-H, Random, 95% CI)-0.01 [-0.08, 0.06]

 3 Admission to hospital for respiratory illness11789Risk Difference (M-H, Random, 95% CI)0.00 [-0.02, 0.03]

    3.1 Vaccinated and unvaccinated patients
11789Risk Difference (M-H, Random, 95% CI)0.00 [-0.02, 0.03]

 4 Deaths from influenza or its complications22140Risk Difference (M-H, Random, 95% CI)-0.01 [-0.05, 0.03]

    4.1 Vaccinated patients
1178Risk Difference (M-H, Random, 95% CI)-0.04 [-0.11, 0.03]

    4.2 Unvaccinated patients
1173Risk Difference (M-H, Random, 95% CI)-0.03 [-0.11, 0.04]

    4.3 Vaccinated and unvaccinated patients
11789Risk Difference (M-H, Random, 95% CI)0.00 [-0.00, 0.01]

 
Table 1. Potter 1997

SVPVSVP0S0PVS0P0

Suspected viral illness24587559

Influenza-like illness2201923

Pneumonia7141618

Deaths from pneumonia10152423

All deaths25255642

 S0P0: staff and patients not vaccinated
S0PV: staff not vaccinated, patients vaccinated
SVPV: staff and patients vaccinated
SVP0: staff vaccinated and patients not vaccinated