| Methods |
Double‐blind RCT. Therapeutic trial |
| Participants |
UK, both sexes. 274 episodes treated with vitamin C; 329 placebo |
| Interventions |
4 g/d vitamin C for the first 2.5 days of illness |
| Outcomes |
Duration (Analysis 4.1) and severity (Analysis 5.1) |
| Notes |
— |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Random sequence generation (selection bias) |
Low risk |
Randomised |
| Allocation concealment (selection bias) |
Low risk |
Double‐blind |
| Blinding of participants and personnel (performance bias)
All outcomes |
Low risk |
Double‐blind |
| Blinding of outcome assessment (detection bias)
All outcomes |
Low risk |
Double‐blind |
| Incomplete outcome data (attrition bias)
All outcomes |
Low risk |
|
| Vitamin C and placebo indistinguishable? |
Low risk |
"the tubes with 'placebo treatment', contained inert substances of identical appearance and taste" |
