Table 3. Summary of findings (GRADE assessment of quality of evidence).

Summary of findings
Number of studies	Study design	Risk of bias	Inconsistency	Indirectness	Imprecision	Other considerations	Number of patients	Quality
Rate of infection
2	Cohort	Not serious	Not serious	Not Serious	Serious	No: publication bias, large effect, plausible confounding, dose response gradient	Intervention total: 79 807, Control total: 33 792	⨁⨁LOW a,b
Detection of resistant organisms without an infection or changes to flora or microbiota
3	1 RCT and 2 cohort studies	Serious	Not serious	Not serious	Serious	No: publication bias, large effect, plausible confounding, dose response gradient	Intervention total: 36, Control total: 45	⨁VERY LOW c,d,e,f,d,g

Explanations
a. Selection bias: students selected from one university campus.
b. Imprecise estimates: wide 95% confidence intervals.
c. Selection bias: patients not randomised to treatment.
d. Confounding factors not reported or incorporated in analysis.
e. Follow-up inconsistent between treatment groups.
f. Confidence intervals not reported and small sample size.
g. No 95% confidence intervals reported: predominantly numbers and percentages reported.

GRADE = Grading of Recommendations Assessment, Development and Evaluation; RCT = randomised controlled trial.