Background: Widespread voluntary medical male circumcision in Africa could avert an estimated 3·436 million HIV infections and 300,000 deaths over the next 10 years. Most Zambian men have expressed little interest in the procedure. We tested the effect of the Spear and Shield intervention designed to increase demand for voluntary medical male circumcision among these hard-to-reach men.

Methods: This cluster randomised controlled trial was done between Feb 1, 2012, and Oct 31, 2014, in Lusaka, Zambia, where HIV prevalence is 20·8%. 13 community health centres were stratified by HIV voluntary counselling and testing rates and patient census, and randomly assigned (5:5:3) to experimental (the intervention), control, or observation-only conditions. Community health centre health-care providers at all 13 sites received training in voluntary medical male circumcision. Eligible participants were aged at least 18 years, HIV-negative, uncircumcised, and had not proactively requested or planned for voluntary medical male circumcision at the time of enrolment. Trial statisticians did not participate in randomisation. After voluntary counselling and HIV testing, participants were recruited; female partners were invited to participate. The primary outcomes at the individual level were the likelihood of voluntary medical male circumcision by 12 months post-intervention, and condom use after voluntary medical male circumcision among participants receiving the intervention. The trial is registered with ClinicalTrials.gov, number NCT01688167.

Findings: 800 uncircumcised HIV-negative men (400 in the experimental group, 400 in the control group) were enrolled. 161 participants in the experimental group and 96 in the control group had voluntary medical male circumcision (adjusted odds ratio 2·45, 95% CI 1·24-4·90; p=0·02). Condom use was examined in participants who had voluntary medical male circumcision and reported sexual activity within 1 month of a post-circumcision assessment (88 in the experimental group and 64 in the control group). Condom use over time increased in the experimental group (p=0·03) but not in the control group (p=0·2). One patient died in each group; no adverse events related to study participation were reported.

Interpretation: Comprehensive HIV prevention programmes can increase the demand for and uptake of voluntary medical male circumcision services.

Funding: US National Institutes of Health/National Institute of Mental Health (R01MH095539).