| Study characteristics |
| Methods |
Prospective cohort study conducted in Italy during the 1978 to 1979 influenza season. Authors investigated an outbreak in a nursing home; individual cards were reviewed. Follow‐up period was 1 November 1978 to 31 May 1979. Throat swab and paired sera specimens were obtained from residents. |
| Participants |
196 nursing home residents (86 treated and 110 controls, all included in the analysis), 60 years or older |
| Interventions |
Parenteral influenza vaccine: A/Texas/1/77; A/USSR/90/77; B/Hong Kong/8/73. Matching between vaccine and circulating strains is unknown. |
| Outcomes |
Positive culture or 4‐fold antibody titre increase with or without symptoms. Only symptomatic cases were included in the analysis. |
| Notes |
Poor reporting of methods; no confounders control. The circulating strain was related to B/Hong Kong/5/72. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
High risk |
C ‐ Inadequate |
