| Study characteristics |
| Methods |
Prospective cohort study conducted in Minneapolis, USA during the 1990 to 1991 influenza season, in the community. Data source was the managed care organisation database. Follow‐up period was 1 October 1990 to 31 March 1991. The rate was adjusted for age, sex, health status, pneumococcal vaccination. |
| Participants |
25,532 members of a medical care programme continuously enrolled for the 1‐year period (11,483 treated and 14,049 controls, all included in the analysis), 65 years or older |
| Interventions |
Parenteral influenza vaccine. 3% of vaccinees and 1% of unvaccinated received pneumococcal vaccination. Vaccine strains matched the circulating strain. |
| Outcomes |
Hospitalisation from pneumonia and influenza (ICD 480‐487), hospitalisation from all respiratory conditions (ICD 460, 462, 465‐466, 480‐487, 490‐96, 500‐518), hospitalisation from congestive heart failure (ICD 428), death from all causes (not reported) |
| Notes |
The season was an epidemic one. Data were extracted by rates reported in tables. Quantitative analysis with adjusted rates was not performed because data reported and statistical model used were not homogeneous to those reported in the other studies. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
Unclear risk |
B ‐ Unclear |
