HIV Transmission Risk ‘Essentially Zero’ with Full Suppression of HIV Viral Load with ART

HIV Transmission Risk ‘Essentially Zero’ with Full Suppression of HIV Viral Load with ART

The findings of a study on HIV transmission has confirmed that the risk of passing on HIV through unprotected anal sex is virtually zero when HIV viral load is fully suppressed through the use of antiretroviral therapy (ART) drugs. The findings of the study raise hopes that it will be possible, through the use of ART, to prevent new infections and end the current HIV/AIDS epidemic. If all infected individuals are treated with ART drugs, no further infections would occur.

The purpose of the study was to determine the risk of HIV transmission risk between sexual partners, where one partner was HIV positive and was receiving ART treatment and the couples were engaging in condomless sex. The first phase of the PARTNER study was conducted on both heterosexual and gay couples, with the PARTNER2 study extending the study with an exclusive focus on gay couples.

During the studies, both partners were questioned during study visits about sexual practices and the HIV-negative partner underwent an HIV test. The viral load of the HIV positive partner was also tested. Data was only included if the HIV-negative partner had not undergone pre-exposure prophylaxis or post-exposure prophylaxis and if the viral load of the HIV positive partner was lower than 200 copies per mL at the most recent visit.

In cases where the HIV-negative partner had contracted HIV, an anonymised phylogenetic analysis was performed to compare HIV-1 pol and env sequences in both partners to determine whether the HIV-positive partner had transmitted HIV.

The PARTNER2 phase of the study was conducted between 2010 and 2017 on 972 gay couples. 782 of those couples were ultimately included in the study, which corresponded to 1,593 couple-years and 76,088 incidences of unprotected anal sex. 288 of the HIV negative men who took part in the study reported having had unprotected sex with other partners.

During the course of the study there were 15 new HIV infections, yet none of those infections was phylogenetically linked to within-couple transmissions, demonstrating the risk of transmission of HIV from an infected partner with viral load suppression was effectively zero. The study confirms the message that undetectable equals untransmittable.

The study reflects the results of the earlier PARTNER study which showed that the risk of HIV transmission between heterosexual couples when one partner has HIV and has viral load suppressed using ART was also virtually zero.

“Increased efforts must now focus on wider dissemination of this powerful message and ensuring that all HIV-positive people have access to testing, effective treatment, adherence support and linkage to care to help maintain an undetectable viral load,” said UCL Professor Alison Rodger, co-author of the paper. Currently there are an estimated 7,800 people in the UK with undiagnosed HIV.

“The PARTNER study has given us the confidence to say, without doubt, that people living with HIV who are on effective treatment cannot pass the virus on to their sexual partners. This has incredible impact on the lives of people living with HIV and is a powerful message to address HIV-related stigma,” said Dr Michael Brady, medical director at the Terrence Higgins Trust.

The paper – Risk of HIV transmission through condomless sex in serodifferent gay couples with the HIV-positive partner taking suppressive antiretroviral therapy (PARTNER): final results of a multicentre, prospective, observational study – was recently published in the journal The Lancet. DOI: 10.1016/S0140-6736(19)30418-0

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