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Treatment as Prevention (TasP): What is TasP and How Does it Affect Me?


Posted on Wednesday, November 02, 2016

What is an Undetectable Viral Load?

HIV treatment can reduce a person’s viral load – the amount of virus in blood and other bodily fluids – until it is ‘undetectable’, unable to be measured by current standard lab tests. Having an undetectable viral load is not a cure for HIV. There is still HIV present in the body but it cannot be measured. Importantly, recent research shows it cannot be passed on to other people.

What is Treatment as Prevention?

Relying on an undetectable viral load to prevent passing on HIV is called Treatment as Prevention. Recent research has shown that there is negligible risk of passing on HIV if a person has an undetectable viral load. Data released from the PARTNER Study in 2016 found there were no HIV transmissions between 888 sero-discordant heterosexual and gay couples – who between them had condomless sex an estimated 58,213 times – where the HIV Positive partner had a viral load under 200 copies/ml.

A couple may rely on an undetectable viral load as a means of HIV prevention if the following conditions are met:

  • Viral load must have been undetectable for at least 6 months. This is measured by a viral load test which measures the amount of virus in a person’s blood. While the amount of virus present in other fluids such as semen or vaginal fluids may differ, recent research shows that an undetectable viral load indicates that there is negligible risk of HIV transmission.
  • Medication must be taken as prescribed. Strict adherence to medication is important in achieving and maintaining an undetectable viral load. Missed doses can lead to medication being less effective, increasing your viral load and the possibility of developing resistance to the drug you are taking.
  • There are no other STIs. For people with multiple partners regular STI checks are important.

Making Choices about HIV Prevention

Treatment as Prevention is viewed as being a reliable protection against HIV. Some couples choose to rely on Treatment as Prevention for HIV prevention. Others prefer the reassurance that comes with combining an undetectable viral load with condoms. Some couples may rely on condoms but use Treatment as Prevention at specific times in their life, such as when they want to conceive a baby. Increasingly doctors are reluctant to prescribe measures such as PrEP for sero-different couples as a prevention method if the HIV positive partner has an undetectable viral load and good adherence to medication.

While HIV medication can reduce the chance of passing on HIV to negligible it does not prevent other STIs. It is important to use condoms to prevent other STIs and have regular STI checks if you are having sex with multiple partners or if you are unaware of your partner’s STI status. Contraception is also important if you wish to prevent pregnancy. It is also important to be aware that not everyone living with HIV will be able to reduce their viral load to undetectable. In that case condoms and PrEP are alternative methods of HIV prevention.

If you need further help in making decisions about HIV prevention our Peer Support Officer at Straight Arrows can be a good person to talk to, as can your HIV doctor.