Factors associated with sexually transmitted reinfections, number of sexual partners and condom use among previously infected young people

Background: Sexually transmitted infections (STIs) are prevalent in young people. Digital interventions promoting safer sexual behaviours are low-cost and scalable. We use data from a randomised controlled trial of one such potential intervention (safetxt) to investigate factors associated with STI reinfection and risky sexual behaviours.

Methods: We use data from 6248 young people with STIs recruited from 92 UK sexual health clinics. Multivariable logistic regression models were developed with the outcomes: reinfection, condom use at last sex and number of sexual partners (≤1 or >1) at 1 year. A pre-specified variable selection process assessed effects of sociodemographic and sexual behaviour factors measured at trial baseline.

Results: Factors associated with reinfection included sexuality, ethnicity, baseline diagnosis of gonorrhoea and chlamydia, index of multiple deprivation, whether the participant and/or the last new partner tested before sex. Risk factors for condom use at last sex and number of sexual partners included sexuality and education level. The multivariable models had good calibration but poor discrimination.

Conclusions: In this large sample with good representation across social and ethnic groups, we identified patient characteristics associated with higher risk of reinfection. Improved understanding of factors associated with reinfections and higher-risk sexual behaviours can aid development of interventions.Trial Registration: ISRCTN64390461.