| Study characteristics |
| Methods |
Prospective cohort study conducted in Japan during the 1998 to 1999 influenza season in 9 nursing homes. Follow‐up period was the epidemic period. Efficacy assessment was also performed by vaccination rate in residents and HCWs, physical impairment, sex, age, and health status of residents. Throat swabs were obtained from ill individuals; medical charts were reviewed. |
| Participants |
699 residents in 9 nursing homes (331 treated and 368 controls, all included in the analysis). The vaccinated group had more underlying diseases. |
| Interventions |
Parenteral influenza vaccine: A/Beijing/262/95; A/Sydney/5/97; B/Mie/1/93. Vaccine strains matched circulating strains (good match). |
| Outcomes |
Clinically defined ILI (fever + cough or coryza or sore throat) occurring during the epidemic period |
| Notes |
The circulating strain was A/Sydney. Influenza virus exposure was confirmed in all 9 facilities. Outbreaks were demonstrated in only 4 homes. No other respiratory viruses were isolated. Data were extracted by RRs reported in tables. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
Unclear risk |
B ‐ Unclear |
