New study challenges assumptions about PrEP, condom use and STIs

Angus Molyneux | Policy Analyst, Australian Federation of AIDS Organisations (AFAO)

PrEP has emerged as a highly effective HIV prevention tool for gay and bisexual men and other people at risk of acquiring HIV. However, PrEP has not been accepted by all, mainly due to fears that its use will lead to further increases in other STIs among gay and bisexual men. This belief has generally been based on the assumption that people using PrEP will be less likely to use condoms, which are effective at preventing the transmission of both HIV and other STIs.

However, a recent study published in the Journal of the American Medical Association has shown that while there has been a 20 per cent increase in STIs among Victorian PrEP users, there was no link between this rise and less frequent condom use.

Data drawn from the Victorian PrEP trial PrEPX by Alfred Health and the Burnet Institute led to the findings, which showed that the acquisition of an STI among PrEP users was not significantly influenced by condom use. Rather, the findings showed the number of casual partners and whether an individual engaged in group sex was a more significant predictor of STI acquisition.

Interestingly, the study also showed that STIs diagnosed among the cohort were mostly contained among one quarter of study participants. This quarter made up the majority of diagnoses and had high rates of reinfection with an STI.

The authors of the study noted that ‘the lack of association with condoms and clustering of STIs in a small group of participants suggested that commencing PrEP may be associated with unknown or unmeasured factors that drive STI risk, such as changes in the size and constituents of sexual networks or other unmeasured sexual behaviours’.

Another recent study also found that while PrEP use may lead to increased STI incidence, quicker diagnosis and treatment due to increased testing among PrEP users may actually lead to an overall decrease in STI prevalence among gay and bisexual men.

While condoms remain an effective HIV and STI prevention tool, the authors of the most recent study noted that the findings suggest STI prevention campaigns should not focus solely on condom use and should also be promoting frequent STI testing in order to reduce the time between STI acquisition and treatment.

The study’s finding that consistent condom use was not associated with decreased STI risk challenges assumptions about PrEP and condom use. This, alongside the known fact that condoms only have partial efficacy to prevent bacterial STI transmission, and that condom use for oral sex is very infrequent among gay men, shows that the way we conceptualise STI prevention in the context of scaled up PrEP use will be critical going forward.