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Studies show an increase in STI infections among PrEP users


Recent studies show evidence that during follow-up periods with doctors, there was an increase in the proportion of participants reported engaging in condomless receptive anal sex with at least 10 partners, condomless sex with an HIV-positive partner or a partner of unknown HIV status, and never using condoms during anal sex.

Over the last four years there has been a lot of speculation around the increases in bacterial sexually transmitted infections (STIs) is associated with the promotion of pre-exposure prophylaxis (PrEP) and condom-less sex for participants.

Australia had its first pilot studies of PrEP in 2014, it was given regulatory approval in early 2016 and began to reimburse most of its cost in March 2018.

Uptake has been rapid in Melbourne (the capital of the state of Victoria) – 6% of gay men were using PrEP in January 2015, rising to 18% in January 2018.

Many of those taking PrEP are participants in PrEPX, an implementation study at ten clinics in a range of locations. The study’s primary objective is to see if the use of PrEP is associated with a reduction in HIV infections across the state, but the conference presentation gave interim findings on the study’s secondary outcome – sexually transmitted infections.

Almost all;

  • 98% are gay and bisexual men, their median age is 34 years,
  • 48% had had condomless receptive anal sex in the three months before enrolling
  • 28% had used PrEP before.

During follow-up of a little more than a year, 52% had no STIs. STIs were highly concentrated in a minority of PrEP users who had repeat infections – 25% of participants had two or more infections accounting for 76% of infections. Thirteen per cent of participants had three or more infections, accounting for 53% of infections.

The most common infections were chlamydia and gonorrhoea. However, incidence was greatly increased for men who took PrEP for the first increased by 48% in people taking PrEP for the first time, which introduces a ‘detection bias’.

The main behavioural factors which were associated with STIs were having more sexual partners and having group sex more frequently. Using condoms more or less often did not make any difference to STI rates. This suggests that interventions to reduce repeat STIs in PrEP users should focus more on partner numbers and on group sex than on condom use.

The research does not contain any data on STI rates of non-PrEP users, who are at greater risk of infections. More education and awareness campaigns about safe-sex and PrEP is needed to put stigma and shame back in the closet.


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