Reducing sexually transmitted infections amongst those at highest risk: The Halo randomised controlled trial
Infections with a predominantly sexual mode of transmission
Intervention (Halo plus usual care): Multi-component digital intervention to increase correct and consistent condom use. Control arm (usual care): Usual care in this instance is 1) the usual testing (and if relevant, follow-up treatment) of chlamydia and gonorrhoea, and 2)provision of basic information on STIs and condoms. The latter is typically present on internet STI self-sampling websites, including those provided by Preventx Ltd, where participants will have been recruited. To provide an ‘intervention experience’ to participants in the control arm, and to ensure that participants in both arms receive identical‘usual care’, this basic information is presented within both the intervention and control websites. Halo also contains the additional content that is being testing via the RCT. Sample: Preventx Ltd provides web-based STI testing services via three STI self-sampling websites (SH.UK, Freetest.me, SHL.UK) to over 75 local authority areas in England. 3576 users of these STI self-sampling websites aged 16-24, residing within participating local authority areas, will be invited to participate in the RCT. Sample size calculation: The trial has been designed to detect a reduction of chlamydia positivity from 10% to 6.5% i.e. 3.5 percentage points. To have 90% power (α=0.05) to obtain the projected difference in the comparative analysis, 1353 (2,706 total) participants per treatment group are required. The recruitment target and the size of the sampling pool required to achieve this have been calculated based on the levels of recruitment and retention observed in the fRCT. Attrition (for primary outcome) was 24.3% at 12 months. To allow for this, the baseline sample needs to be 1788 per treatment group (1353/0.757; 3576 participants in total). During the feasibility RCT (fRCT), 1.5% of all Preventx users shown the study advert were recruited. A sampling pool of 238,400 users of SH.UK/Freetest.me/SHL.UK aged 16-24 years is therefore required to achieve this targ
1. Young people aged 16-24 years old at baseline 2. Living in one of the local authority areas participating in the trial 3. Ordered an STI self-sampling kit that includes tests for chlamydia and gonorrhoea from SH.UK, FreeTest.me or SHL.UK websites 4. Access to a personal mobile phone and the internet 5. Able to read/understand the English language
1. Unlikely to have penetrative sex (penis in either vagina or anus) over the trial period 2. Do not feel able to commit to the trial over the next 12 months