| Study characteristics |
| Methods |
Case‐control study conducted in Spain during the 1994 to 1995 influenza season, in the community. Data sources were: hospital emergency logs and records; structured interview. Follow‐up period was 15 November 1994 to 31 March 1995. Cases were people admitted to hospital for pneumonia; controls were admitted to hospital in the same week for acute abdominal surgical condition or trauma. |
| Participants |
249 non‐institutionalised people (94 cases and 166 controls were identified; 83 and 166 were included in analysis, respectively), 65 years or older |
| Interventions |
Parenteral influenza vaccine. Vaccine strains matched the circulating strain. |
| Outcomes |
Hospitalisation for pneumonia; pneumonia was clinically defined and radiologically confirmed |
| Notes |
The study controls for confounders in analysis: health status, age, socio‐economic factors. The season probably had low epidemic levels. Quantitative analysis was also performed. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
Unclear risk |
B ‐ Unclear |
