801 participants were enrolled. Risk behaviours were assessed with an interviewer-administered questionnaire at 6-month intervals. We assessed change from enrolment to the first 6-month assessment pre-unblinding and between enrolment and at least 6 months post-unblinding on all participants with comparable data. A one-time unblinding risk perception questionnaire was administered post-unblinding.
A decrease in participants reporting unprotected sex was observed in both measured time periods for men and women, with no differences by treatment arm. At 6 months (pre-unblinding), 29.6 % of men and 35.8 % of women reported changing from unprotected to protected sex (p < 0.0001 for each). Men (22 % ) were more likely than women (14 % ) to report behaviour change after unblinding (p = 0.009). Post-enrolment, 142 (45 % ) of 313 previously uncircumcised men underwent medical circumcision. 663 participants completed the unblinding questionnaire. More vaccine (24.6 % ) as compared to placebo recipients (12.0 % ) agreed that they were more likely to get HIV than most people (p < 0.0001), and attributed this to receiving the vaccine.
We did not find evidence of risk compensation during this clinical trial. Some risk behaviour reductions including male circumcision were noted irrespective of treatment allocation.