| Study characteristics |
| Methods |
Case‐control study conducted in Manitoba, Canada during the 1982 to 1983 influenza season, in the community. Data source was insurance claim records. Follow‐up period was 1 December 1982 to 28 February 1983. Cases were admitted to the hospital with a lower respiratory tract condition as first diagnosis; community controls were matched for age, sex, and residence. |
| Participants |
10,471 non‐institutionalised people, 70% were older than 65 years (2619 cases and 7828 controls, all included in analysis) |
| Interventions |
Parenteral influenza vaccine. Vaccine strains matched the circulating strain. |
| Outcomes |
Hospitalisation from a lower respiratory tract condition (ICD 466, 480‐487, 490‐496, 500‐519), deaths from any respiratory condition, deaths from all causes. Data about deaths were not reported. |
| Notes |
Circulating strain: A/Bangkok/1/79‐like. The season was an epidemic one. The study controls for confounders in analysis: health status. Quantitative analysis was also performed. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
Low risk |
A ‐ Adequate |
