Swiss HIV Study Confirmed in Canada: Treatment Eliminates Transmission

 A few years ago, we reported on this blog a Swiss Study that concluded that when HIV-positive individuals receive treatment that reduces their viral loads to "undetectable" levels (less than 40 copies per ml blood at the time), the transmission of the virus to negative partners was virtually impossible.  The study was so certain in its results that it lead to changes in Swiss law concerning criminalizing HIV+ individuals having sex.

That news was received with mix results, as the 30 year old "wear a condom!" message, long losing steam but still a cornerstone of government-funded HIV programs, began to be replaced with a common sense message of universally treating the virus as a better prevention approach. The move to "attacking the virus" rather than "restraining the individual" has not been met without resistance, especially by HIV agencies used to receiving government funding merely by placing baskets of condoms around town and telling people to 'wrap up.'

Now, a more comprehensive study validating the Swiss findings was released in Canada this past month.


According to this review of multiple studies, released by National AIDS Treatment Advocacy Policy (NATAP),  heterosexual serodiscordant couples have an almost non-existent risk of HIV transmission if the HIV-positive partner has an undetectable viral load as a consequence of successful antiretroviral (ARV) therapy,  Presenting their findings at the Third International Workshop on HIV and Women in Toronto, researchers pooled data from six different studies of serodiscordant heterosexual couples, including the famous HPTN 052, which found a 96 percent risk reduction due to ARV therapy.

Three of the studies provided data on HIV transmission rates, ARV history and viral load of the HIV-positive partner. These studies included a combined 991 couples with 2,064 person-years of follow-up. The researchers found a transmission rate of 0.0 per 100 person years.

Three additional studies, including HPTN 052, had information on just rates of transmission and treatment history, covering 5,233 couples. Factoring in these studies with the other three, the researchers found a pooled transmission risk of 0.14 per 100 person years. In other words, if 1,000 serodiscordant couples in which the HIV-positive partner is on ARV therapy with an undetectable viral load had sex for one year, about one or two of the HIV-negative partners would become infected with the virus.

All four of the transmissions in the six studies took place before six months had passed since the HIV-positive partner began ARVs and therefore may not have yet reached an undetectable viral load. Taking this into account, the researchers conducted another analysis excluding the data from these transmissions. In this case, the risk of transmission was also 0.0 per 100 person years.

To read the conference abstract, click here.