Comparison 30. B ‐ Non‐monetary incentives: Addition of societal benefit message vs usual follow‐up.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
30.1 Retention	1	1950	Risk Difference (M‐H, Fixed, 95% CI)	‐0.00 [‐0.04, 0.04]