| Study characteristics |
| Methods |
Experimental study conducted in the Netherlands during the 1991 to 1992 influenza season, randomised, double‐blind, placebo controlled; randomisation scheme was stratified according to health status. Follow‐up period was 48 hours after vaccination. Adverse reactions were self reported on postal questionnaire completed 4 weeks after vaccination |
| Participants |
1838 not known as belonging to a high‐risk group (927 treated and 911 controls; 23 and 9 dropped out, respectively), 60 years or older |
| Interventions |
Parenteral influenza recommended vaccine: A/Singapore/6/86; A/Beijing/357/89; B/Beijing/1/97; B/Panama/45/90 |
| Outcomes |
Local: swelling, itching, warm feeling, pain when touched, constant pain, discomfort. Systemic: fever, headache, malaise, other complaints |
| Notes |
Harms were reported for all participants and by risk condition. Data regarding all participants were included |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Random sequence generation (selection bias) |
Low risk |
Adequate description |
| Allocation concealment (selection bias) |
Low risk |
Adequate description |
| Blinding (performance bias and detection bias)
All outcomes |
Low risk |
Described as placebo controlled, but no additional information was available |
| Incomplete outcome data (attrition bias)
All outcomes |
Low risk |
Adequate description of follow up and attrition |
