Summary of individual patient data-based studies
| Study | Study period | Population | VARI | PD (cases (n)) | Methods | Main findings |
| Edwards et al 17 | 2005– 2009 | All ages Northern Territory, Australia | IFV | IPD (n=346) | Using data from notifiable diseases system, relative risk (RR) of IPD calculated in ≤4 w after IFV compared with background risk | RR=112.5 (48.9–224.8) |
| O’Brien et al 25 | 1995– 1996 | <18 y Iowa, USA | ILI IFV A | Severe PP (n=13) | Case–control design: case from children with severe PP, three controls per case selected, from friends of cases or from the same primary care practice, matched by age (within 1 y of the case). ILI history (7–28 d within admission) investigated by telephonic interview and IFV A convalescent serology collected. | OR (ILI history)=12.4 (1.7–306), OR (IFV A convalescent serology)=3.7 (1.0–18.1) |
| Stensballe et al 29 | 1996– 2003 | All ages Denmark | RSV non-RSV | IPD (n=7787) | Prospective cohort study: two exposure groups, RSV and non-RSV respiratory infection hospitalisations within 30 d | RR for RSV=7.1 (3.6–14.3), RR for non-RSV=4.5 (2.0–10.0) |
d, day(s); IFV, influenza virus; ILI, influenza-like illness; IPD, invasive pneumococcal disease; PD, pneumococcal disease; PP, pneumococcal pneumonia; RSV, respiratory syncytial virus; VARI, viral acute respiratory infection; w, week(s); y, year(s).