Table 2.
Baseline characteristics of included studies
| Author, year | Country | Study design | Influenza season(s) | Age-group (yrs) or risk group | Age (yrs), range or mean (± SD) | % male | Data sources | Identification of outcomes | Study size (n) |
|---|---|---|---|---|---|---|---|---|---|
| Bond et al., 2012 [17] | US | Cohort | 2005/06 | Patients with ESRD | V, 60.6 (15.2) | V, 52.5 | 3 ESRD Networks, records of the US Renal Database (USRDS) | All-cause death through ESRD death notification form | 20,220 (without pneumococcal vaccine) |
| UV, 57.9 (15.9) | UV, 50.8 | ||||||||
| Campitelli et al., 2010 [7] | Canada | Cohort | 8 seasons between 1996 and 2007 | Elderly ≥ 65 | V, 75.3 (6.6) | V, 40.8 | National health surveys data linked to Ontario Health Insurance (OHIP) and Discharge Abstract (CIHI) databases | Registered persons database and ICD-9/-10 admission codes | V, 14,512 |
| UV, 74.2 (6.7) | UV, 40.7 | UV, 11,410 | |||||||
| Foster et al., 1992 [18] | US | Case–control (matched) | 1989/90 | Elderly ≥ 65 | V, 65-94+ | V, 50.8 | Databases of participating hospitals | Hospital discharge ICD-9 codes | Cases, 721 |
| UV, 65-94+ | UV, 47.3 | Controls, 1786 | |||||||
| France et al., 2006 [34] | US | Cohort | 1995/96-2000/01 | Women and their newborns | V, 30.8 (5.5) | NA | Health maintenance organization (Kaiser Permanante and Group Health Cooperative) | ICD-9 codes for medically attended acute respiratory illnesses in infants | V, 3160 |
| UV, 29.7 (5.5) | UV, 37,969 | ||||||||
| Groenwold et al., 2009 [19] | Netherlands | Cohort | 1995/96-2002/2003 | Elderly ≥ 65 | V, 75 (median) | V, 39.4 | GPRD of University Medical Center Utrecht | ICPC coding system | V, 37,501 |
| UV, 74 (median) | UV, 35.2 | UV, 13,405 | |||||||
| Hottes et al., 2011 [20] | Canada | Cohort | 2000/01-2005/06 | Elderly ≥ 65 | V, 75 (median) | V, 43 | Manitoba Immunization Monitoring System (MIMS) and Manitoba health policy database | All-cause mortality or hospital admission ICD-9/-10 codes | 139,185 (00/01) to 140,735 (05/06) |
| UV, 73 (median) | UV, 44 | ||||||||
| Jackson et al., 2006 [35] | US | Cohort | 1995/96-2002/3 | Elderly ≥ 65 | V, 51 % >74 | V, 42.7 | Health maintenance organization (Group Health Cooperative) | All-cause mortality or hospital ICD-9 discharge codes | 72,527 |
| UV, 46 % >74 | UV, 41.9 | ||||||||
| Jackson et al., 2002 [21] | US | Cohort | 1992-1996 | Patients with nonfatal MI | All subjects, 64 (median) | among ≥ 65: | Health maintenance organization (Group Health Cooperative) | Hospital discharge ICD-9 codes, confirmed by chart review | V, 1016 |
| UV, 362 | |||||||||
| V, 47 | |||||||||
| UV, 59 | |||||||||
| Jackson et al., 2008 [5] | US | Case–control (matched) | 2000/1-2001/2 | Elderly 65-94 | Cases, 62 % >74 | cases, 51 | Health maintenance organization (Group Health Cooperative) | ICD-9 code for CA pneumonia and validation using hospital records | Cases, 1173 Controls, 2346 (1838 V, 508 UV) |
| Johnstone et al., 2012 [33] | 40 countries | Cohort | 2003/04-2006/7 | Elderly ≥ 65 with VD or diabetes | Mean (4 seasons) | Range (4 seasons) | Clinical databases from two RCTs (ONTARGET- and TRANSCEND-trial) | Outcomes adjudicated by independent committee using clinical data | 31,546 |
| V, 67-68 | V, 72-73 | ||||||||
| UV, 65-66 | UV, 67-70 | ||||||||
| Liu et al., 2012 [22] | Taiwan | Cohort | 2002-2006 | Elderly > 65 with heart disease | V, 74.8 (6.3) | V, 58.3 | National Health Research Institute-released cohort dataset | ICD-9 codes for heart diseases | V, 2760 |
| UV, 75.7 (7.0) | UV, 51.8 | UV, 2288 | |||||||
| Mangtani et al., 2004 [16] | UK | Cohort | 1989/90-1998/99 | Elderly ≥ 65 | Not reported | Not reported | General practice research database (GPRD) | ICD-9 codes for acute respiratory illnesses; all respiratory-related deaths | Person-years: influenza season, 419,748 summer, 692,415 |
| McGrath et al., 2012 [23] | US | Cohort | 1997-1999 and 2001 | Patients with ESRD | Mean (4 seasons) | Range (4 seasons) | Medicare claims from the US Renal Data System (USRDS) | All-cause death through ICD-9 codes; Medicare claims from the USRDS | 107,465 (1997) to 126,699 (2001) |
| V, 62.3-63.9 | V, 52.2-53 | ||||||||
| UV, 60.3-61.7 | UV, 50.4-51.6 | ||||||||
| Nicol et al., 2008 [24] | US | Cohort | 2002/03-2005/06 | Adults (students) | V, 25.2 (7.9) | V, 25.5 | Internet-based survey | Self-reported occurrences of ILI and health care use | 12,795 |
| UV, 23.3 (6.3) | UV, 29.4 | ||||||||
| Nicol et al., 2009 [25] | US | Cohort | 2006/07 | Adults, 50-64 | Not reported | V, 24 | Internet-based survey | Self-reported occurrences of ILI and health care use | 479 |
| UV, 16 | |||||||||
| Ohmit et al., 1995 [26] | US | Case–control (matched) | 1990/91-1991/92 | Elderly ≥ 65 | not reported | not reported | Admission and discharge data of 21 participating hospitals | ICD-9 hospitalization code for pneumonia/influenza | Cases, 1557 Controls, 3401 |
| Omer et al., 2011 [27] | US | Cohort | 2004/05-2005/06 | Women and their newborns | V, 18.3 % < 19 | NA | Georgia Pregnancy Risk Assessment Monitoring System (PRAMS) | PRAMS database (questionnaire or interview) | V, 578 |
| UV, 3590 | |||||||||
| UV, 14.5 % < 19 | |||||||||
| Örtqvist et al., 2007 [15] | Sweden | Cohort | 1998/99-2000/01 | Elderly ≥ 65 | V, 51 % >74 | V, 41.3 | Population register (via national identification number) | ICD-9/-10 codes and cause of death register | 260,155 |
| UV, 51 % >74 | UV, 39.0 | ||||||||
| Schembri et al., 2009 [28] | UK | Cohort | 1998-2006 | Adults > 40 with COPD | V, 27 % > 69 | V: 42.8 | The Health Improvement Network database (THIN), covering data of general practices | Diesease classification codes of THIN databases (“Read codes”) | V, 9679 |
| UV, 31,062 | |||||||||
| UV, 12 % > 69 | UV: 42.8 | ||||||||
| Sung et al., 2014 [29] | Taiwan | Cohort | 2000-2007 | Elderly ≥ 55 with COPD | V, 20 % >74 | V: 58.7 | Reimbursement claims from National Health Insurance Research Database (NHIRD) | ICD-9 codes for acute MI or angina pectoris with invasive therapy | V, 3027 |
| UV, 17 % >74 | UV: 60.8 | UV, 4695 | |||||||
| Tessmer et al., 2011 [30] | Germany | Cohort | 2002-2006 | Adults with pneumonia (CAP) | V, 67.6 (14.5) *1 | V: 57.2 | National Community Acquired Pneumonia Competence Network (CAPNET) | CAPNET database entries | V, 1721 |
| UV, 3279 | |||||||||
| UV, 55.7 (19.0) | UV: 52.5 | ||||||||
| Vila-Córcoles et al., 2007 [31] | Spain | Cohort | 2002-2005 | Elderly ≥ 65 | V, 51 % > 74 | V, 44.3 | Databases of Primary Health Care Centres (PHCC) | ICD-9 codes of PHCC and Civil Registry Offices | V, 6051 |
| UV, 5189 | |||||||||
| UV, 38 % > 74 | UV, 43.6 | ||||||||
| Wong et al., 2012 [32] | Canada | Cohort | 2000/01-2008/09 | Elderly ≥ 65 | V, 75.5 (6.6) | V, 43.8 | Ontario Health administrative databases | ICD-9/ -10 codes of databases and registered persons database | 1,297,051 (00/01) to 1,527,364 (08/09) |
| UV, 74.5 (6.8) | UV, 43.6 |
SD standard deviation, V vaccinated, UV unvaccinated, ESRD end-stage renal disease, ICD international classification of disease, CHD chronic heart disease, GPRD general practice research database, ICPC international classification of primary care, MI myocardial infarction, CA(P) community acquired (pneumonia), VD vascular disease, ONTARGET-trial Ongoing Telmisartan Alone and in Combination With Ramipril Global EndPoint Trial, TRANSCEND-trial Telmisartan Randomized Assessment Study in ACE Intolerant Subjects with Cardiovascular Disease, ILI influenza-like illness, COPD chronic obstructive pulmonary disease