| Study characteristics |
| Methods |
Prospective cohort study conducted in Italy during the 1990 to 1991 influenza season; medical charts, hospital records, and death certificate archives were reviewed. Follow‐up period was 1 December 1990 to 30 April 1991. 110 participants were tested for serological follow‐up. Throat swabs were obtained from ill residents. |
| Participants |
242 nursing home residents (169 treated and 73 controls, all included in the analysis; 77 and 33 were tested for serological follow‐up, respectively), 55 to 99 years old |
| Interventions |
Parenteral influenza vaccine: A/Guizhou/54/89; A/Singapore/6/86; B/Yagamata/16/88. Vaccine strains matched the circulating strains. |
| Outcomes |
Clinically defined ILI (fever + at least 2 of the following: cough, coryza, sore throat, myalgia, headache, shivering), hospitalisation for ILI, hospitalisation for all respiratory illness, deaths from respiratory illness |
| Notes |
Circulating strain: B/Yagamata‐like. Vaccinated and control groups were roughly comparable as underlying disease: vaccinated participants had more chronic respiratory diseases. The influenza season was relatively mild. Data were reported by health status. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
Low risk |
A ‐ Adequate |
