| Study characteristics |
| Methods |
Retrospective cohort study conducted in Michigan, USA during the 1982 to 1983 influenza season, in 6 nursing homes. Throat swab and paired sera specimens were obtained from some residents; medical records were reviewed. Follow‐up period was 10 December 1982 to 4 March 1983. |
| Participants |
458 residents in 6 nursing homes without outbreak (339 treated and 119 controls, all included in the analysis) |
| Interventions |
Parenteral influenza vaccine: A/Bangkok/79; A/Brazil/78; B/Singapore/79. Vaccine strains matched circulating strains. |
| Outcomes |
Clinically defined ILI (fever 37.8 °C or greater + cough, coryza, or sore throat), deaths occurring within 2 weeks of onset of ILI |
| Notes |
Cohorts were comparable as age and level of nursing care. Amantadine was not used. The circulating strain in the community was A/Bangkok/1/79‐like, but laboratory confirmation was not available in the homes. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
Low risk |
A ‐ Adequate |
