The adherence-monitoring IVR design is a modification of the established pod-IVR platform that was developed specifically for controlled vaginal delivery of drug combinations. The pod-IVR has been applied to delivery of small molecule ARV drugs for HIV [18, 19, 23–25] and HSV [18, 26] prevention as well as to vaginal delivery of monoclonal antibodies  and bacterial probiotics . The pod-IVR consists of a silicone elastomer scaffold containing individual embedded drug pods that act as independent delivery devices. The adherence-monitoring module may be incorporated in the same manner as the drug pods, and drug release from the device will be unaffected. The dimensions of the prototype adherence module described here was chosen to be small enough to fit within a pod-IVR containing an expanded section as shown in Fig 1A, but large enough to allow manual soldering rework and other modifications during device development to be easily carried out. The electronics layout has subsequently been further miniaturized to a circuit board size of 14 mm × 5.1 mm that will fit within the dimensions of a standard pod-IVR (8 mm cross-sectional diameter, 56 mm outer ring diameter). This is also the size of the dapivirine IVR that has recently completed Phase 3 clinical trial . Future efforts will focus on further miniaturization of the electronics module and the incorporation of adherence-monitoring functionality into pod-IVRs delivering ARV combinations.