A study of serodiscordant (positive and negative) heterosexual couples in 2011 found that being on treatment reduced the risk of HIV being passed on by 96%. This study, known as HPTN 052, has proven (IAS 2015) without doubt that effective treatment reduces or virtually eliminates onwards transmission of HIV. Since then, NAPWHA’s ‘Start the Conversation’ campaign and ACON’s ‘Ending HIV’ campaign have both made earlier treatment part of their message about HIV prevention.
On current knowledge, the following things need to happen for treatment to work as prevention:
Having an STI can cause increased viral load in genital tissues and secretions, even when viral load in samples of your blood is low. If you are sexually active and want to rely on treatment as prevention, ask your GP to include sexual health care in your appointments for HIV monitoring (CD4 and viral load).
Studies of treatment as prevention (TasP) suggest it is at least as effective as condoms in preventing HIV transmission between heterosexual and gay male couples. Many couples will feel reassured by this additional layer of protection on top of their use of condoms. But what about using TasP instead of condoms?
The public health law in Victoria requires people living with conditions like HIV to take ‘all reasonable steps’ to prevent HIV infection. If the requirements of TasP (see above) are met, the additional benefit from using condoms would be minimal, and it may not count as a ‘reasonable’ step to take.
However, if a person living with HIV knew or thought they had either an STI or non-suppressed viral load, either using condoms, or the negative partner using PrEP, would be reasonable steps to prevent infection and meet the requirements of public health law.
None of the studies conducted to date have suggested that the viral load of a positive partner or either partner having an STI reduces the effectiveness of Pre-Exposure Prophylaxis.