Simon Lewin is a health systems researcher at the MRC and at the Norwegian Institute of Public Health. His work is largely within the field of implementation research, including systematic reviews of complex health interventions; the evaluation of strategies for changing professional and consumer behaviours; and methods for qualitative evidence synthesis. He is currently working on a new approach for assessing how much confidence to place in findings from qualitative evidence syntheses; on evidence-based strategies for improving communication about childhood vaccination; and on supporting research evidence use in low- and middle-income countries. He is a joint Co-ordinating Editor for the Cochrane Effective Practice and Organisation of Care Group.