| Study characteristics |
| Methods |
Authors investigated an outbreak in a nursing home in Washington, USA during the 1988 to 1989 influenza season; residents' records and hospital charts were reviewed. Follow‐up period was 29 January 1989 to 1 March 1989. Throat swabs were obtained from a sample of acutely ill residents; paired sera were obtained from 63% of both ill and well residents. |
| Participants |
109 nursing home residents (48 treated and 61 controls; 45 and 52 included in the analysis, respectively), 58 to 105 years old. Groups were similar in age, gender, and level of care required. |
| Interventions |
Parenteral influenza vaccine: A/Taiwan; A/Sichuan; B/Victoria. Vaccine strains probably matched circulating strains. |
| Outcomes |
Outbreak‐associated cases: clinically defined ILI (fever + cough) or laboratory‐confirmed influenza (4‐fold increase in antibody titre), pneumonia, hospitalisation from ILI or pneumonia, deaths from ILI or pneumonia |
| Notes |
Vaccination was not offered to staff. Positive specimens showed a diagnostic titre rise to A/Sichuan, but no virus was isolated; matching was only hypothetic. Amantadine was not used. Laboratory‐confirmed cases were analysed by intention‐to‐treat. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
Low risk |
A ‐ Adequate |
