The most extensive study on prevention treatment carried out among gay men, bisexuals and other men who have sex with men (MSM) has provided more evidence to support the message “undetectable is equal to intransmissible” or “I = I”. The final results of the PARTNER 2 study, published in The Lancet, show that, after eight years of follow-up, none of the 1,000 serodiscordant couples of gay, bisexual and other MSM men had any HIV transmission. In all these couples the member with HIV was in virological suppression thanks to the use of antiretroviral treatment. The couples, during the 8 years of follow-up, had accumulated more than 70,000 sexual relations without a condom.
In the first phase of the study, especially in heterosexual men, HIV transmissions were not detected when the viral load was below 200 copies / mL in 1,166 serodiscordant couples. Due to the low presence of couples of gay men, bisexuals and other MSM led to the design of the second phase, PARTNER 2, which only included couples of this type, since it is the population group most vulnerable to HIV. The first results of PARTNER 2 have already been very promising.
This study included 972 serodiscordant couples of gay men, bisexuals and other MSM from 14 European countries between 2010 and 2017. In the case of Spain, a total of 10 centers in Catalonia, Comunidad de Madrid, Andalucía, Galicia and Comunidad Valenciana They included participants. All the included couples reported having sex without a condom.
Every six and twelve months the participants completed questionnaires about their sexual practices, the non-HIV partner did an HIV test and the member with HIV performed a viral load test. In the study, virological suppression status was defined as having a viral load below 200 copies / mL. Faced with a positive result, the researchers carried out a genetic analysis of the HIV of both partners to establish whether there was a relationship between the two and, therefore, that HIV transmission had taken place within the couple.
Altogether, the participants totaled a total of 76,088 anal sex practices without a condom. 37% of participants without HIV reported having sexual practices outside of the couple. In the study, no cases of HIV transmission were detected within the stable couple.
The data provided by the study allowed the researchers to estimate confidence intervals regarding the risk of transmission during a punctual sexual practice without a condom. Thus, the risk of higher transmission would be 0.23% in the case of sexual relations without condoms in general and 0.57% in the case of receptive anal sex with ejaculation.
The 15 HIV infections detected during the study were not attributed – after the phylogenetic analysis of HIV of both partners – to a transmission within the couple, but were due to sexual practices that the member initially without HIV had outside of the couple.
The results of the PARTNER study support the recommendation that HIV physicians speak proactively with their HIV patients about “I = I =” at different times of care, including, but not limited to, the time of diagnosis, upon initiation treatment (to promote adherence), and when viral load reaches undetectability, so that they can take together with their partners the best decisions about their sexual and reproductive health.