Investigation of mediating effects of sexual behaviours on the effect of a novel digital intervention on sexually transmitted reinfections: secondary analysis of a randomised controlled trial
- 1Universidad de Alcala
Abstract
BackgroundPreventing sexually transmitted re-infections brings health benefits and can be significantly less costly than treating their sequelae. Safetxt is a potential novel digital intervention developed to promote safer sexual behaviours. However, a recent randomised controlled trial of safetxt found no effect on reinfection at 1 year (OR 1.13, 95%CI: 0.98-1.31). We investigated if safetxts effect was mediated through sexually risky behaviours.
MethodsWe used data from 6248 young people with STIs from 92 UK sexual health clinics. The direct and indirect effects of safetxt on reinfection were estimated using the counterfactual approach. Condom use at last sexual encounter, number of sexual partners and STI testing were assessed as mediators. These were analysed singly and together, using regression models and a formal weighting approach. The assumptions of each approach were considered and tested. Analyses were repeated in the subgroup showing the most promising effect of safetxt: men who have sex with men or with men and women (MSM/MSMW).
ResultsNo evidence was found for the total, indirect or direct effects differing from the null. Despite not being significant, for MSM/MSMW, some of safetxts effect on reducing reinfection was identified as being offset through its effect on number of sexual partners.
ConclusionsThere was no evidence that safetxts effect on reinfection was mediated through changes in sexually risky behaviours. Adaptations to specifically target these behaviours are unlikely to improve safetxts overall effect. However, improving safetxts effect on the number of sexual partners a participant has may improve its effect for MSM/MSMW.
What is already known on this topicThe safetxt intervention did not result in a reduction in reinfection rate among 16-24 year olds diagnosed with chlamydia, gonorrhoea or non-specific urethritis in the UK. However, safetxt did result in increased condom use at 1 year. Results of the safetxt trial were most promising for men who have sex with men or with men and women (MSM/MSMW).
What this study addsDisaggregating the effect of a novel digital intervention on sexually transmitted reinfections allows understanding of the mechanisms through which it acts. Investigators hypothesised that safetxts true effect was being mediated through changes in other sexual behaviours. This study shows there is no evidence of this from the safetxt trial.
How this study might affect research, practice or policyAll estimated effects were non-significant. Overall safetxts effect in the primary trial analysis was not due to mediation through condom use, number of sexual partners or STI testing. In MSM/MSMW, safetxts effect was identified as being reduced through number of sexual partners. Alterations to improve safetxts effect on the number of sexual partners a participant has could be considered with the aim of improving its overall effect on reinfection for MSM/MSMW.
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BibTeX
@misc{landray2026investigation,
title = {{Investigation of mediating effects of sexual behaviours on the effect of a novel digital intervention on sexually transmitted reinfections: secondary analysis of a randomised controlled trial}},
author = {I. Landray and J. Carpenter and C. Free},
howpublished = {medRxiv},
year = {2026},
month = aug,
doi = {10.64898/2026.08.29.26361435},
url = {https://www.medrxiv.org/content/10.64898/2026.08.29.26361435v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Investigation of mediating effects of sexual behaviours on the effect of a novel digital intervention on sexually transmitted reinfections: secondary analysis of a randomised controlled trial
AU - I. Landray
AU - J. Carpenter
AU - C. Free
PY - 2026
DA - 2026/08/29
PB - medRxiv
DO - 10.64898/2026.08.29.26361435
UR - https://www.medrxiv.org/content/10.64898/2026.08.29.26361435v1
AB - BackgroundPreventing sexually transmitted re-infections brings health benefits and can be significantly less costly than treating their sequelae. Safetxt is a potential novel digital intervention developed to promote safer sexual behaviours. However, a recent randomised controlled trial of safetxt found no effect on reinfection at 1 year (OR 1.13, 95%CI: 0.98-1.31). We investigated if safetxts effect was mediated through sexually risky behaviours. MethodsWe used data from 6248 young people with STIs from 92 UK sexual health clinics. The direct and indirect effects of safetxt on reinfection were estimated using the counterfactual approach. Condom use at last sexual encounter, number of sexual partners and STI testing were assessed as mediators. These were analysed singly and together, using regression models and a formal weighting approach. The assumptions of each approach were considered and tested. Analyses were repeated in the subgroup showing the most promising effect of safetxt: men who have sex with men or with men and women (MSM/MSMW). ResultsNo evidence was found for the total, indirect or direct effects differing from the null. Despite not being significant, for MSM/MSMW, some of safetxts effect on reducing reinfection was identified as being offset through its effect on number of sexual partners. ConclusionsThere was no evidence that safetxts effect on reinfection was mediated through changes in sexually risky behaviours. Adaptations to specifically target these behaviours are unlikely to improve safetxts overall effect. However, improving safetxts effect on the number of sexual partners a participant has may improve its effect for MSM/MSMW. What is already known on this topicThe safetxt intervention did not result in a reduction in reinfection rate among 16-24 year olds diagnosed with chlamydia, gonorrhoea or non-specific urethritis in the UK. However, safetxt did result in increased condom use at 1 year. Results of the safetxt trial were most promising for men who have sex with men or with men and women (MSM/MSMW). What this study addsDisaggregating the effect of a novel digital intervention on sexually transmitted reinfections allows understanding of the mechanisms through which it acts. Investigators hypothesised that safetxts true effect was being mediated through changes in other sexual behaviours. This study shows there is no evidence of this from the safetxt trial. How this study might affect research, practice or policyAll estimated effects were non-significant. Overall safetxts effect in the primary trial analysis was not due to mediation through condom use, number of sexual partners or STI testing. In MSM/MSMW, safetxts effect was identified as being reduced through number of sexual partners. Alterations to improve safetxts effect on the number of sexual partners a participant has could be considered with the aim of improving its overall effect on reinfection for MSM/MSMW.
ER -