Treatment as prevention (TasP) is a concept in public health that promotes treatment as a way to prevent and reduce the likelihood of HIV illness, death and transmission from an infected individual to others. Expanding access to earlier HIV diagnosis and treatment as a means to address the global epidemic by preventing illness, death and transmission was first proposed in 2000 by Garnett et al. The term is often used to talk about treating people that are currently living with human immunodeficiency virus (HIV) and acquired immune deficiency syndrome (AIDS) to prevent illness, death and transmission. Although some experts narrow this to only include preventing infections, treatment prevents illnesses such as tuberculosis and has been shown to prevent death. In relation to HIV, antiretroviral therapy (ART) is a three or more drug combination therapy that is used to decrease the viral load, or the measured amount of virus, in an infected individual. Such medications are used as a preventative for infected individuals to not only spread the HIV virus to their negative partners but also improve their current health to increase their lifespans. When taken correctly, ART is able to diminish the presence of the HIV virus in the bodily fluids of an infected person to a level of undetectability.World Health Organization (WHO) (2012) 'Antiretroviral treatment as prevention (TASP) of HIV and TB'[pdf] Consistent adherence to an ARV regimen, monitoring, and testing are essential for continued confirmed viral suppression. Treatment as prevention rose to great prominence in 2011, as part of the HPTN 052 study, which shed light on the benefits of early treatment for HIV positive individuals.
Evidence through observational, ecological and clinical trials reveal positive results in regards to the implementation of antiretroviral drugs as preventative measures against HIV transmission. Progress in scaling up access to treatment is brisk, and as of 2023 there are over 29 million people receiving antiretroviral therapy. Challenges to scaling access to treatment include cost and drug resistance.
TasP's legitimacy has influenced the World Health Organization's (WHO) 2015 shift from "test and wait" to "test and treat" recommendation, focusing on alerting as many people as possible of their HIV status through testing and starting them on ART treatment, regardless of their viral load or CD4 count.World Health Organization (WHO) (2015) 'Guideline on when to start antiretroviral therapy and on pre-exposure prophylaxis for HIV' The diminished rate of new HIV infections brought about by these strategies are marked progress towards UNAIDS' 90-90-90 and 95-95-95 target to eliminate HIV/AIDS as a public health crisis by 2030.UNAIDS (2014/2017) '90-90-90: An ambitious treatment target to help end the AIDS epidemic'[pdf] However, key populations in countries in Africa, Asia, and the Middle East may still have lower access to treatment.UNAIDS (2016) 'Prevention Gap Report'[pdf] Understanding whether marginalized groups have access to testing and treatment are often hampered by harsh laws that do not allow for the accurate collection of data regarding these communities. Estimates of the number of people who are men who have sex with men, female sex workers, and/or drug users are very difficult to ascertain, rendering understanding diagnosis and access to treatment levels also difficult to determine.
TasP and test and treat to maximize access to early treatment is now the global standard for HIV prevention.
HIV Prevention Trials Network clinical trial 052 Early work by Quinn in Uganda demonstrated that transmission was reduced by over 90% when people living with HIV were on treatment and virally suppressed. Observational evidence accumulated and the Attia meta analysis supported the 2008 Swiss Statement that said that those suppressed on treatment had little or no chance of transmission. Many experts, citing the Bradford Hill criteria, accepted this observational data. However, others called for randomized control trials.
The HIV Prevention Trials Network conducted a clinical trial, HPTN 052, that analyzed the effectiveness of antiretroviral drugs on the HIV-1 virus. 1,783 HIV sero-discordant couples, or couples that consist of an HIV-positive individual and an HIV-negative partner, from nine countries were a part of the study, 97% of the couples being heterosexual. In August 2011, the HIV Prevention Trials Network concluded that the likelihood of transmission between the couples who were provided early antiretroviral therapy reduced by 96%. When the trial completed, the overall reduction percentage of HIV-1 transmission between couples who were treated early with ART or received the delay-ART treatment was 93%. The study's purpose was to reveal that HIV-1 viral transmission can be prevented through treatment, leading many regions to incorporate a treatment as prevention plan into their public health policy for responding to HIV.
Implementation Treatment as prevention has been used as a form of controlling the spread of HIV since the mid-1990s, initially in the context of preventing the transmission of the virus from mothers to their children. Research in 1994 revealed how the drug zidovudine can reduce vertical transmission. The testing and treatment of HIV-positive mothers during pregnancy, childbirth, and breastfeeding has since led to the reduction of the risk of transmission by up to 95%.World Health Organization (WHO) 'Mother-to-child transmission of HIV' [accessed 23 May 2016] A program for offering ARVs for life to any HIV-positive pregnant woman called "Option B+" served as a precursor to the "test and treat" strategy that is now being rolled out in various countries.Kalua, T. et al (2017) 'Lessons Learned From Option B+ in the Evolution Toward "Test and Start" From Malawi, Cameroon, and the United Republic of Tanzania' Journal of Acquired Immune Deficiency Syndromes Assessments of the Option B+ program are able to aid in the improvement and further establishment of "test and treat".
From 2013 to 2018, the global number of people receiving ARV treatment rose by a third, and now is at 23 million people.UNAIDS (2016) 'Get on the Fast-Track' [pdf] This is a result of increased use of "test and treat". In 2015, about one fourth of the 148 countries informed about national treatment plans had initiated the WHO's "test and treat" approaches, and 44 more countries pledged to implement them by the end of 2016. The five-year HPTN 071 "PopART" study is currently examining the efficacy of TasP in 21 communities throughout South Africa and Zambia.Cori, A. et al (2014) 'HPTN 071 (PopART): A Cluster-Randomized Trial of the Population Impact of an HIV Combination Prevention Intervention Including Universal Testing and Treatment: Mathematical Model' PLOS One 9(1):e84511 PopART is focused on the advantages and downfalls of providing free voluntary HIV testing in combination with instant treatment for those who test positive.London School of Hygiene & Tropical Medicine 'HPTN 071 (PopART)' This study has a scope of about 1 million residents, making it the largest executed test of "test and treat".HPTN (2017) 'HPTN 071 (PopART) at CROI 2017: HPTN 071 (PopART) at CROI 2017: Mid-Study Successes and Challenges' [pdf]
Challenges and risks associated with Treatment as Prevention While TasP has a huge potential to prevent the further spread of HIV worldwide, the major barrier to implementing TasP is lack of political will. Specifically, estimates suggest that only around 60% of all resources for HIV go towards ensuring diagnosis and treatment while the rest is spent on other priorities. In some African countries multiple billions of dollars have been allocated with some only achieving 60-70% ART coverage. Global HIV control priorities often include 90-90-90 and 95-95-95 (proxies for TasP coverage), however, TasP is often not included when calling for increased efforts in preventing and ending the epidemic. Many of the most vulnerable populations may not be seeing these benefits as a result of a social and political climate that is deterrent to seeking testing and treatment, in addition to making it difficult to stick with the ARV regimen. With this, antiretroviral therapy should be implemented within every country's public health policy, yet challenges and risks are faced when such implementation is put into action. While vulnerable populations often have difficulty accessing services, it is unknown what proportion of MSM, FSW and DUs are on ART due to uncertainties in determining estimating the numbers of people and the understandable reluctance for many people to disclose whether they are in these groups when accessing services.
Overall cost of treatment For many countries, especially low- and middle-income countries, the overall cost of treatment in the 1990s and early 2000s was too expensive for infected patients to afford it. In addition, individuals with low incomes in United States struggle to pay high prices set by pharmaceutical companies for antiretroviral drugs. As a result, it was implausible for a global treatment system or policy to be put into place since no universal HIV/AIDS test and medication regimen existed and due to technology and wealth disparities worldwide. However, with the advent of rapid HIV testing (including self testing), viral load testing, and effective ART regimens at less than $100 per year treatment scale up (read widespread implementation of TasP) is now a reality in many settings.
Side effects caused by ART Newer ART regimens are largely side effect free and side effects are no longer a major barrier to starting treatment. Additionally, newer regimens are almost 100% resistance free and can translate into lifelong effective therapy. In the past antiretroviral drugs can also cause patients to experience various side effects including becoming nauseated or developing gastrointestinal pains and issues, as a results of medications at times being too toxic for a specific individual. In addition, in low and middle income countries (LMICs), an increase in the number of side effects expressed in a country leads to the underdeveloped health care systems of said country having to use their limited funds to account for service delivery costs of medications to counter the newly inflicted problems among infected individuals.
HIV-1 drug resistance HIV drug resistance has also come to the forefront of worries in regards to how effective TasP can be against the spread of the virus. The widespread global use of ARVs is feared to lead to an increase in drug resistance as a result of interrupted treatment and a lack of adherence. Despite these fears widespread resistance threatening the efficacy of ART has not emerged despite tens of millions of people being on treatment in the harshest conditions. Likewise fears of non-adherence also proved to be overblown.
Developed countries, when first discussing the implementation of ART in the developing world, believed that the allowance of third-world countries to have early access to antiretroviral drugs would potentially lead to the development of drug resistance. Recently, such resistance has developed in third-world countries as a result of medication combinations failing to diminish the viral load of HIV-1 in infected individuals, the lack of existence of virological testing to discover such failures in patients in these regions of the world and the lack of variants of medication regimens to suppress the evolution of the infection.