| Study characteristics |
| Methods |
Experimental study conducted in Virginia, USA during the 1968 to 1969 influenza season. 4 arms: parenteral vaccine, aerosol vaccine, both, placebo. Methods are described in another article. |
| Participants |
266 elderly psychiatric patients (90 in the parenteral arm, 89 in the aerosol arm, 88 in the arm with both administrations, 87 in the placebo arm) |
| Interventions |
Monovalent inactivated A2 Hong Kong influenza vaccine. Vaccine strains probably matched the circulating strains. |
| Outcomes |
Clinically defined ILI (fever + 1 or 2 respiratory symptoms or at least 2 systemic symptoms, lasting longer than 1 day; 3 respiratory symptoms or 2 respiratory symptoms + 2 systemic symptoms, lasting longer than 2 days); laboratory‐confirmed influenza |
| Notes |
The study year was an epidemic one; circulating strain was A2 HK. |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Random sequence generation (selection bias) |
Unclear risk |
Insufficient details provided. |
| Allocation concealment (selection bias) |
Unclear risk |
Insufficient details provided. |
| Blinding (performance bias and detection bias)
All outcomes |
Unclear risk |
Insufficient details provided. |
| Incomplete outcome data (attrition bias)
All outcomes |
Unclear risk |
Insufficient details provided. |
