Table 1 Summary of the 116 included studies - study designs and level of evidence

Good

Randomised controlled trial (RCT)

9

[23, 24, 36, 37, 42, 43, 88, 90],[106]

Fair

Non-RCT comparison of strategies or groups

14

[17, 25, 41, 59, 61, 62, 79, 83],[104, 109, 110, 116, 126, 128]

Poor

Descriptive study (with quantitative data, e.g., % of target group recruited, often single strategy pre-post)#

48

[14–16, 18–22],[26, 27, 30, 33, 35, 38–40],[44–47, 49–51, 53],[54, 58, 65–67];[71, 75, 76];[77], [81, 84, 85, 87, 91, 95–97],[99, 112, 113, 117, 119, 120, 125, 129]

Poor

Qualitative study (e.g., focus groups or interviews)

16

[29, 32, 60, 64, 68, 72, 73, 86],[89, 92, 94, 101, 108, 122, 124, 127]

Poor

Case studies without data

28

[28, 31, 34, 48, 52, 55–57, 63, 69],[74, 78, 80, 82, 93, 98, 100, 102],[103, 105, 107, 111, 114, 115, 118, 121],[123]