| Study characteristics |
| Methods |
Retrospective cohort study conducted in Spain during the 1991 to 1992 influenza season, in the community. Data sources were: the health centre register, death certificate archives, hospital records. Follow‐up period was 7 months after vaccination. People were excluded if they did not approach the centre in the last 3 years. |
| Participants |
1965 community‐dwelling elderly enrolled in a health centre (779 treated and 1186 controls, all included in the analysis), 65 years or older, mean age 73.5 years |
| Interventions |
Parenteral influenza vaccine. Vaccine strains probably matched the circulating strain. |
| Outcomes |
Hospitalisation from cardio‐respiratory causes, death from all causes. Only deaths from all causes are included in analysis. |
| Notes |
The study controls for confounders in analysis (age, health status, home care). The season had low epidemic levels. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
Unclear risk |
B ‐ Unclear |
