| Study characteristics |
| Methods |
Case‐control study conducted in England, during the 1989 to 1990 influenza season, in the community. Data sources were: death certificates, general practitioner records. Follow‐up period was 4 November 1989 to 23 February 1990. Cases died from influenza during the 1989 epidemic; controls died in the same period a year later and were matched for age, sex, and residence |
| Participants |
1092 people 16 years or older; 412 cases and 1256 controls were identified; 315 and 777 were included in the analysis, respectively |
| Interventions |
Parenteral influenza vaccine. Vaccine strains matched the circulating strain |
| Outcomes |
Certified influenza death |
| Notes |
2 exposure definitions were used: current vaccinees and previous vaccinees (vaccinated between 1985 and 1989) the first was used; pneumococcal vaccination was very unlikely; circulating strain was A/England/308/89. The season was an epidemic one. The study controls for confounders in analysis: health status, previous vaccination. Quantitative analysis was also performed. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
Unclear risk |
B ‐ Unclear |
