Table 5. Risks associated with controlled human infection with Schistosoma mansoni.

Risk	Inherent risk score		Total inherent risk	Controls	Residual risk score		Total risk post control
	Likelihood	Impact			Likelihood	Impact
Symptoms related to infection	Common	Major	20	1)  Slow dose escalation in modest increments 2)  Frequent follow up visits and collection of adverse events. 3)  Clinical assessment and routine safety lab. 4)  Symptomatic treatment with corticosteroids or abrogating infection with praziquantel (which kills adult worms) if needed. 5)  Abrogate infection with artesunate (which kills immature forms)	Common	Moderate	15
Symptoms related to treatment with praziquantel	Common	Moderate	15	1)  Take praziquantel with food 2)  Clinical assessment, reassurance, symptomatic relief if needed	Common	Minor	10
Misunderstanding of the nature of CHI-S studies	Likely	Critical	20	1)  Education of community leaders, opinion makers and regulators 2)  Work with community advisory board 3)  Education of potential volunteers using tested materials 4)  Informed consent verified with tests of comprehension	Possible	Major	12
Inappropriate remuneration leading to coerced participation	Possible	Moderate	9	1) Formative research to determine appropriate remuneration	Unlikely	Moderate	6

Likelihood was scored as almost certain/common, 5; likely, 4; possible, 3; unlikely, 2; rare, 1. Impact was scored as critical, 5; major, 4; moderate, 3; minor, 2; insignificant 1.