Anderson 1975b.

Methods	See Anderson 1975a. This arm used vitamin C capsules
Participants	152 vitamin C
Interventions	See Anderson 1975a
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
Allocation concealment (selection bias)	Low risk
Blinding of participants and personnel (performance bias) All outcomes	Low risk
Blinding of outcome assessment (detection bias) All outcomes	Low risk
Incomplete outcome data (attrition bias) All outcomes	Low risk
Vitamin C and placebo indistinguishable?	Low risk