| Study characteristics |
| Methods |
Experimental study conducted in Minneapolis, USA during the 1988 to 1989 influenza season, randomised, double‐blind, placebo‐controlled cross‐over trial. Follow‐up period was 7 days after vaccination. Symptoms were assessed by phone interview. |
| Participants |
672 outpatients (336 treated and 336 controls were included in the analysis), 65 years or older |
| Interventions |
Parenteral influenza recommended vaccine: A/Taiwan/1/86; A/Sichuan/2/87; B/Victoria/2/87 |
| Outcomes |
Cough, coryza, fatigue, malaise, myalgia, headache, nausea, sore arm, disability, feverish without further description |
| Notes |
Placebo was saline injection. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Random sequence generation (selection bias) |
Unclear risk |
Randomisation method described. |
| Allocation concealment (selection bias) |
Unclear risk |
Allocation concealment not described. |
| Blinding (performance bias and detection bias)
All outcomes |
Low risk |
Probably acceptable since placebo was a saline injection |
| Incomplete outcome data (attrition bias)
All outcomes |
Unclear risk |
Short‐term follow‐up for most outcomes was by phone, but unclear how complete data were for longer‐term outcomes. |
