Design and methods for the Carrageenan-gel Against Transmission of Cervical Human papillomavirus (CATCH) study: A randomized controlled trial.

Human papillomavirus (HPV) infection, a common sexually transmitted infection, is causally associated with cervical cancer. Vaccination against HPV provides protection; however, HPV vaccines are exclusively prophylactic. Carrageenan, an extract from red algae, demonstrated potent anti-HPV activity in in vitro and animal studies. We describe the protocol for the Carrageenan-gel Against Transmission of Cervical Human papillomavirus (CATCH) study, an ongoing randomized controlled trial among sexually active young females, aimed at evaluating the efficacy of a carrageenan-based gel in reducing type-specific incidence (i.e. new detections of HPV) and prevalence (i.e. absence of a previously detected HPV) of genital HPV infections as well as participant adherence to the intervention. The CATCH study is a phase IIB double-blind randomized placebo-controlled trial. Eligible women 18 years and older are randomized 1:1 to the carrageenan-containing gel or placebo gel arm. For the first month, participants use the study gel intra-vaginally every other day, and over the 12-month study period, prior to and after each act of vaginal intercourse. At each study visit (months 0, 0.5, 1, 3, 6, 9, 12), participants provide a self-collected vaginal sample and record information on sexual activities, adherence, and adverse events using a computerized questionnaire. The primary outcomes are incident and prevalent type-specific cervicovaginal HPV infection. The primary analyses are based on intention-to-treat whereas per-protocol analyses are conducted based on measures of adherence. Trial registration: ISRCTN96104919.