| Study characteristics |
| Methods |
Prospective cohort study conducted in the USA during the 1996 to 1997 influenza season, in the community. Data source was a 3 managed care organisation database. Follow‐up period was 5 October 1996 to 3 May 1997. |
| Participants |
122,974 members of a medical care programme continuously enrolled for the 1‐year period (71,005 treated and 51,969 controls, all included in the analysis), 65 years or older |
| Interventions |
Parenteral influenza vaccine. Vaccine matched the circulating strain. |
| Outcomes |
Hospitalisation from influenza and pneumonia (ICD 480‐487), death from all causes |
| Notes |
Identical to Hak 1. Odds ratios adjusted for age, sex, site, health status were presented. Frequencies data were not available. To perform quantitative analysis adjusted data were used. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
Low risk |
A ‐ Adequate |
