| Study characteristics |
| Methods |
Retrospective cohort study conducted in Italy during the 1991 to 1992 influenza season, in the community. Data sources were self administered questionnaire and vaccination registry. Follow‐up period was 1 December 1991 to 29 February 1992. Random samples of vaccinated and control participants were extracted from vaccination and population registries. |
| Participants |
213 community‐dwelling elderly (150 treated and 63 controls; number of participants included in the analysis unknown), 65 years or older |
| Interventions |
Parenteral influenza vaccine. Matching unknown, probably yes according to literature data. |
| Outcomes |
Clinically defined ILI (fever, cough, sore throat, myalgia, headache, weakness) |
| Notes |
Very poor description of methods, poor definitions, data extracted from percentages |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
High risk |
C ‐ Inadequate |
