Table 1.
Characteristics of included studies, patient populations, topic and results of risk of bias assessment
| Reference (Country) |
Study design (population) |
Influenza season (setting) |
Mean (SD) Agea | Gender, % malea | N total | Outcome | Potential bias identified & expected impact (Quality assessmentb) |
|---|---|---|---|---|---|---|---|
| Randomised controlled trials | |||||||
| Chuaychoo et al., 2010 [31] (Thailand) | Open label RCT (Patients with confirmed COPD) |
2006–2007 (1 hospital COPD clinic) |
73 (9) | 90.7% | 75 | Immunogenicity Safety |
No placebo-controlled group; open-label design; self-reported safety outcomes (LOW) |
| Gorse et al., 2004c [32] (US) | Placebo-controlled RCT (Patients ≥ 50 years with confirmed COPD) |
1998–1999 (20 Veterans affairs medical centres) |
67.9 (8.5)/67.8 (8.2) | 98.0/98.4% | 2,215 | Immunogenicity | Serum titres tested in 61 subject; no placebo-controlled/unvaccinated group (ACCEPTABLE) |
| Gorse et al., 2003c [39] | 2,215 | Safety | Self-reported safety outcomes (ACCEPTABLE) | ||||
| Kositanont et al., 2004d [40] (Thailand) | Placebo-controlled RCT (2 doses 1 month apart) (Patients with confirmed COPD) |
1997–1998 (1 hospital COPD clinic) |
67.6 (8)/69.1 (7) | 95.2/93.7% | 123 | Immunogenicity Efficacy |
Self-reported safety outcomes (ACCEPTABLE) |
| Wongsurakiat et al. 2004ad[35] | 125 | Immunogenicity Efficacy |
|||||
| Wongsurakiat et al., 2004bd[38] | 125 | Safety | |||||
| Gorse et al., 1997 [33] (US) |
RCT (Outpatients with confirmed COPD) | (Veterans affairs medical centres) | 65.2 (2.1) | 100% | 29 | Immunogenicity Safety |
Small sample size; no estimate of study power; limited information on patient characteristics; males only (LOW) |
| Observational studies | |||||||
| Nath et al., 2014 [34] (Australia) |
Prospective cohort study (Patients with confirmed COPD) |
2010 (outpatient clinics 1 hospital) |
66.2 (11.0)/54.3 (14.5) | 65.0/57.1% | 34 | Immunogenicity | Small sample size; no estimate of study power; significant differences between groups at baseline; serological response to only one vaccine strain (LOW) |
| Chen et al., 2013e [45] (Taiwan) |
Retrospective, Database study (Patients ≥ 55 years with COPD diagnosed using ICD-9 codes) | 2000–2007 (Taiwan National Health Insurance Research Dataset) |
- | 58.9/53.4% | 25,609 | Effectiveness | Retrospective design; no estimate of study power (ACCEPTABLE) |
| Sung et al., 2014e [46] | ≥55 | 58.7/60.8% | 7,722 | Effectiveness | Retrospective design; estimate of study power (ACCEPTABLE) | ||
| Menon et al., 2008 [43] (India) |
Self-controlled case series (Male patients with confirmed COPD) |
2004–2006 (outpatient department 1 hospital) | 64.8 (8) | 100% | 87 | Effectiveness | Small sample size; no estimate of study power; males only; comparison of different influenza seasons (LOW) |
| Schembri et al., 2009 [42] (UK) | Retrospective, database study (Patients ≥ 40 year registered in the data base with COPD) | 1988–2006 (The Health Improvement Network) |
- | 42.4/42.8% | 40,741 | Effectiveness | Retrospective design; no estimate of study power (ACCEPTABLE) |
| Vila-Córcoles et al., 2008 [41] (Spain) | Prospective cohort study (Community-dwelling ≥65 years olds registered with COPD in clinic record) |
2002–2005 (8 urban health centres) |
74.1 (6.8)/76.3 (6.9) | 73.7/74.5% | 1,298 | Effectiveness | Significant differences between groups at baseline; no estimate of study power (ACCEPTABLE) |
| Ting et al., 2011 [36] (UK) | Retrospective matched cohort study (Patients with confirmed COPD) | 2005 (6 general practices) | 68 (37–89) | 64.8% | 586 | Safety | Retrospective design; sample size calculations performed but details not presented; limited information on patient characteristics; matched pairs of patients, but no results of matching (LOW) |
| Montserrat-Capdevila et al., 2014 [44] (Spain) | Retrospective cohort study (Patients registered with confirmed COPD) |
2001–2002 (1 hospital) |
75.6 (11.7)/57.1 (18.2) | 65.2/60.5% | 1,323 | Effectiveness | Retrospective design; no estimate of study power (ACCEPTABLE) |
| Tata et al., 2003 [37] (UK) | Database study with self-controlled case series (Random sample of patients with COPD using OXMIS and READ codes) | 1991–1994 (Clinical Practice Research Datalink, previously General Practice Research Database) | 65–79 | 63% | 2,100 | Safety | Retrospective design; limited information on patient characteristics (ACCEPTABLE) |
| Wang et al., 2003 [12] (Taiwan) | Retrospective population-based cohort study (>65 years old patients with COPD identified using ICD-9 mortality codes) | 2001 | No data for patients with COPD | 102,698 elderly | Effectiveness | Retrospective database design; no estimate of study power; COPD identified from mortality ICD-9 codes; Reason for risk status not known; limited information on patient characteristics (LOW) | |
N number of subjects, RCT randomised controlled trial, SD standard deviation, UK United Kingdom, US United States, COPD chronic obstructive pulmonary disease, ICD-9 international classification of disease version 9. Confirmed COPD, COPD confirmed according to spirometry criteria
aAge and gender presented as vaccinated/unvaccinated or controls
bStudy quality according to Scottish Intercollegiate Guidelines Network (SIGN) checklists [21]. Studies classified as of low or acceptable quality
cGorse et al., 2004 and Gorse et al., 2003 describe the same RCT
dKositanont et al., 2004, Wongsurakiat et al., 2004a and Wongsurakiat et al., 2004b describe the same RCT, with minor discrepancies in patient characteristics
eIn the study of Sung et al., 2014 a subpopulation of Chen et al., 2013 is used