July 12: To coincide with the IAS Conference, Durban, 2016, the Journal of the American Medical Association (JAMA) has published the first formal results of the PARTNER Study in a special issue devoted to HIV-related matters (Vol. 316, No. 2).
Initially, at the 2014 CROI Conference, the PARTNER study investigators reported their interim (2 year) findings demonstrating zero linked transmissions among sero-discordant couples in the absence of condoms where the partner was taking HIV treatment (QPP also provided an update then https://www.qpp.org.au/latest/un-detectable-un-transmissible-un-ambiguously).
Now in 2016, with longer term follow-up data, this is still the case – ZERO partner linked transmissions occurred after 888 heterosexuals and gay men sero-discordant couples had sex 58,000 times without condoms (with the HIV-positive partner on antiretroviral HIV treatment with viral load less than 200 copies). Specifically, couples reported condomless sex a median of 37 times per year (although some HIV infections did occur outside of the relationship with other sex partners, NONE of the infections where linked to the primary partner on treatment). Now too, the upper 95% confidence interval (CI) for the theoretical (estimated) rate of within-couple transmission during anal sex among MSM with ejaculation has also narrowed from 4.0 (as presented at CROI in 2014) to 2.70 in these new published results.
There are other risks CI calculations within the study for other types of sex (such as vaginal sex, or anal sex among heterosexuals) which show variable confidence measures with the results, but still the observed rate is still actually zero = no transmissions. The overall confidence interval for all people for any type of sex is 0.30, which is significant. The confidence interval is a scientific measure for ‘possible risk’ (i.e. something that may yet be unknown that could increase the risk that the study might be limited by) – despite the overall observed zero rate of infections. The CI can never be zero, but this study demonstrates that it is very close to zero, and confirms that the risk of HIV transmission is negligible when the positive partner is on ARV treatment with suppressed viral load. Additionally, neither the presence of sexually transmitted infections (STIs) nor possible viral load blips between tests had any impact on enabling transmission in this study.
These findings confirm the real-world (observed) effectiveness of treatment as prevention (TasP) in both heterosexual and same-sex male couples, and offer some empowerment to sero-discordant couples (heterosexual and same-sex) to make informed choices around their decisions for condom use. Whether this data will influence casual relationships around issues of HIV disclosure and the law are yet to be seen; but it is worthwhile noting that this (and other prevention studies) have affected policy – whereby Australian Guidelines for Post-Exposure Prophylaxis (PEP) do NOT recommend PEP in cases where a known HIV-positive source has an undetectable viral load (on treatment).