An analysis of previous studies of ways to prevent the transmission of HIV suggests the risk increases over time in a sero-discordant gay couple.
According to a report on the analysis just published by AIDSMAP:
• If no protective measures are taken, there is a 52 percent risk of the HIV negative partner contracting HIV after one year, which adds up to 99.9 percent after ten years.
• If the negative man takes PrEP, the risk is 34 percent after one year, 98 percent after ten years.
• If condoms are used, the risk is 13 percent after one year, 76 percent after ten years.
• If the positive man takes HIV treatment, the risk is three percent after one year, 25 percent after ten years.
• If condoms and PrEP are used, the risk is eight percent after one year, 59 percent after ten years.
• If condoms and HIV treatment are used, the risk is one percent after one year, six percent after ten years.
• If condoms and PrEP and HIV treatment are used, 0.3 percent after one year, three percent after ten years.
AIDSMAP noted that the analysis, conducted by reseachers for the National Center for HIV and the Center for Disease Control and Prevention, is based on mathematical modeling of previous studies, not an actual study itself. And it noted: “The study has a number of limitations. The authors acknowledge that they did not factor in whether the partner on HIV therapy achieved viral load suppression. They also used pessimistic estimates of the efficacy of various prevention strategies.”
A study released earlier in March painted a more optimistic picture for gay men in a sero-discordant relationship in which the HIV positive partner was “undetectable.” Someone who is undetectable has fewer than 200 copies of the HIV virus per one milligram of blood, which indicates that he is being successfully treated for HIV.
That PARTNER Study, conducted by various clinics across Europe, found after two years that there was no incidence of HIV transmission among serodiscordant couples in which the positive partner was undetectable. The researchers reported that at most five percent of HIV negative partners would be infected over ten years, although they said the likely result would be zero.
Those pessimistic estimates are based on assumptions that some gay men using PrEP (pre-exposure prophylaxis, a treatment regimen that requires taking a drug called Truvada daily) and condoms won’t be consistent in their use.