Sperber 1992.

Methods	Double‐blind, placebo‐controlled, experimental colds
Participants	79 inoculated (first cohort 34, second cohort 24 and third cohort 21); 56 colds. Mean age 21.4 years, 52% women. Setting not reported
Interventions	For first cohort, naproxen loading dose of 400 mg followed by 200 mg 3 times daily, and for second and third cohort, naproxen loading dose of 500 mg followed by 500 mg 3 times daily for 5 days
Outcomes	5‐point symptom score. Total cumulative 5‐day score for headache was lower in the naproxen group (0.5 versus 2.5, P value < 0.001)
Notes	1 in the naproxen group and 2 in the placebo group experienced gastrointestinal complaints
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"Participants were randomly assigned to receive..." Comment: insufficient information about the sequence generation process
Allocation concealment (selection bias)	Unclear risk	Comment: insufficient information about the allocation concealment
Blinding (performance bias and detection bias) All outcomes	Low risk	"The study drug and placebo were supplied in identically appearing capsules" Comment: probably done
Incomplete outcome data (attrition bias) All outcomes	Low risk	"Among 87 volunteers completed, 79 were considered evaluable" The reason for exclusion (infected with wild type rhinovirus, not infected, missed dose of study drug) is unlikely to be related to the outcome of the trial (symptomatic improvement of common cold symptoms) Comment: probably done
Selective reporting (reporting bias)	Unclear risk	No protocol, no convincing text
Other bias	Low risk	The study appears to be free of other sources of bias