| Study characteristics |
| Methods |
Authors investigated outbreaks in 14 nursing homes in Wales, UK during the 1991 to 1992 influenza season. Follow‐up period was 15 December 1991 to 28 February 1992. Paired sera specimens were collected from 7 cases in 2 homes. |
| Participants |
466 residents in 14 nursing homes (104 treated and 362 controls, all included in the analysis) |
| Interventions |
Parenteral influenza vaccine. Vaccine strains probably matched circulating strains. |
| Outcomes |
Clinically defined URI (upper respiratory illness: fever, chills, myalgia, cough) |
| Notes |
Very poor reporting. Vaccine strain was assumed to match the circulating strain according to literature data. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
Unclear risk |
D ‐ Not used |
