Economics of HIV/AIDS Transmission, Treatment, and Prevention

At the end of 2011, according to Joint United Nations Program on Human immunodeficiency virus (HIV)/Acquired immunodeficiency syndrome (AIDS) (UNAIDS), an estimated 34 million people were living with HIV worldwide. The number of people dying of AIDS-related causes fell to 1.7 million in 2011, down from a peak of 2.2 million in the mid- 2000s. There were 2.5 million new HIV infections in 2011, including an estimated 390 000 among children. This was 15% less than in 2001, and 21% below the number of new infections at the peak of the epidemic in 1997. Sub-Saharan Africa remains the region most heavily affected by HIV. In 2011, approximately 69% of all people living with HIV resided in sub-Saharan Africa, a region with only 12% of the global population. Sub-Saharan Africa also accounted for 70% of new HIV infections in 2010, although there was a notable decline in the regional rate of new infections. As Africa shoulders the heaviest burden, this article emphasizes evidence from this continent.

The article focuses on the economics of HIV/AIDS and therefore does not emphasize the biomedical determinants of the epidemic. However, it briefly summarizes some of the recent biomedical prevention interventions. The focus of the discussion is on behaviors, economic behaviors, and incentives in particular. For that reason, the article does not address the HIV epidemic among children, even though it constitutes a heavy burden and an important challenge. This article will mainly review the microeconomic aspects of HIV/AIDS.

The article articulates the discussion around the three themes of HIV transmission, prevention, and AIDS treatment. It starts by exploring the determinants of HIV transmission, focusing on behavioral (gender and marriage, serodiscordant couples and multiple partners, and concurrency) and socioeconomic (poverty, education, and occupation) determinants. A short Section ‘(Micro-) Economic Consequences of HIV/ AIDS’ follows. The Section ‘HIV Prevention’ reviews the recent advances in biomedical prevention interventions (male circumcision, treatment for prevention, and preexposure chemoprophylaxis) before discussing behavioral interventions: information and education campaigns (IECs), HIV testing and counseling (HTC), school-based interventions, and conditional cash transfers. The Section ‘AIDS Treatment’ reviews briefly the literature on adherence to treatment before presenting the evidence about the socioeconomic benefits of antiretroviral treatment. Before the Section ‘Conclusion’, the article addresses, at the intersection between AIDS treatment and HIV prevention, the issue of disinhibition behaviors.

Determinants Of HIV Transmission

This article does not focus on the biological determinants of HIV transmission but rather on the behavioral and socioeconomic determinants of HIV infection.

Behavioral Determinants

Gender And Marriage

An alarming demographic trend in developing countries has been the steadily increasing percentage of adolescents and women who are HIV positive. If globally, 50% of all people living with HIV are women, in sub-Saharan Africa, that proportion rises to 61% and young women (15–24 years) are 3–6 times more likely to be infected than men in the same age group. These patterns have been identified as reflecting marriage patterns and risk: women are marrying younger than men and are often initiating sexual activity earlier, but women are also biologically more vulnerable to HIV infection. Several researchers argue that early marriage by females presents an important risk factor for HIV infection that is generally not being addressed and that could be contributing to the increase in HIV among this relatively large segment of the population (almost a third of girls between the ages of 10 and 19 in developing countries marry before their 18th birthday). Using data from 22 Demographic and Health Surveys (DHS) conducted in Africa, Latin America, and the Caribbean, these researchers conclude that two main factors increase the vulnerability of young brides to HIV infection: (1) marriage dramatically increases the frequency of unprotected sex for most young brides and (2) many young brides marry older men, who are more likely to be HIV positive, because of their longer sexual activity.

Another study documents the increased risk of HIV infection for young married females by comparing prevalence data among the partners of young married females and the boyfriends of unmarried females the same age who are seropositive. It reports that in Kenya 30% of male partners of young wives are HIV positive, whereas only 11.5% of partners of unmarried females the same age are seropositive.

Yet another draws the opposite conclusion. The analysis done in this study, based on DHS in Ghana, Kenya, and on cross-country comparisons, suggests that late marriage and a long interval between first sex and first marriage are risk factors for HIV infection. Other researchers use data from five DHS that include HIV testing for a nationally representative sample (Burkina Faso (2003), Cameroon (2004), Ghana (2003), Kenya (2003), and Tanzania (2003–04)) to assess the question empirically. Overall, except in Cameroon, their results do not support the hypothesis that early marriage increases the HIV risk for women. Getting married at an early age does not seem to put young married women at any greater risk of contracting HIV than women their age who do not get married. However, except in Burkina Faso, marriage does not seem to protect women against HIV either.

One study focuses on the risk associated with remarriage. Using DHS nationally representative data from 13 sub-Saharan African countries, it concludes that, in almost all of the countries examined, there are high rates of remarriage and these remarried individuals have significantly higher rates of HIV prevalence than the adult population in general and that of other married individuals. It stresses that this relationship is not necessarily causal, but that remarried individuals constitute a large segment of the population that is highly vulnerable to HIV/AIDS and has not been clearly identified as such by the existing prevention efforts. Using the same data sources, another study also investigates how reported condom use varies within and outside marriage. It reinforces and expands on previous findings that men report using condoms more frequently than women do and that unmarried respondents report that they use condoms with casual partners more frequently than married individuals report using them with their spouses. The study documents that married men from most countries report using condoms with extramarital partners about as frequently as unmarried men report using them with casual partners. Married women from most of the countries included in the study reported using condoms with extramarital partners less frequently than unmarried women reported using them with casual partners. This result is especially troubling because marriage usually ensures regular sexual intercourse, thereby providing more opportunities for a person to pass HIV infection from an extramarital partner to his or her spouse.

Serodiscordant Couples

Recent research on discordant couples (couples in which only one partner is HIV positive) also shed new lights on the dynamics of HIV infection within marriage. In five countries – Burkina Faso, Cameroon, Ghana, Kenya, and Tanzania – an analysis of HIV status among discordant couples yields two findings that challenge conventional notions about HIV transmission. First, in at least two-thirds of HIV-positive couples (couples with at least one HIV-positive partner), only one partner is HIV positive. Second, in close to half of those serodiscordant couples only the woman is positive. These findings have important implications for HIV prevention policies and have been confirmed in a meta-analysis for a larger set of African countries.

A pervasive, if unstated, belief is that males are by and large responsible for spreading the infection among married and cohabiting couples. The results from the analysis of discordant couples suggest, however, that HIV prevention policies should take into account the fact that women are almost as likely to be the infected partner.

Multiple Partners And Concurrency

In terms of behaviors, strong emphasis has been put on the hypothesis that concurrent sexual partnerships have been and remain an important driver of the HIV epidemic, especially in southern and eastern Africa. Concurrency is defined when an act of sex with one partner occurs between two acts of sex with another partner. In a network where people engage in concurrent sexual partnerships, if one person is living with HIV, the virus can spread much more rapidly among the other partners, as at any point in time a larger number of individuals is connected through the sexual network and is susceptible of becoming infected and then transmitting the infection. This network effect is further reinforced by the fact that immediately after becoming infected with HIV, HIV-positive individuals are more infectious and at higher risk of transmitting HIV within their network. Although concurrent sexual partnerships occur everywhere in the world, they might be more prevalent or last longer in southern or eastern Africa, which might be one of the key factors explaining the higher HIV prevalence in those regions. However, the hypothesis that concurrency is one of the main drivers of the HIV epidemic is difficult to establish empirically and there is a debate as to whether the evidence is strong enough to support it. The debate focuses on the measurement of concurrency (recent surveys using improved questionnaire design show reported concurrency to be between 0.8% and 7.6% in sub-Saharan Africa), the assumptions used in mathematical models of concurrency, and on whether a correlation between HIV and concurrency can be established.

Socioeconomic Determinants

Poverty

To what extent is poverty to be blamed for the AIDS epidemic? Globally, the countries hardest hit by the AIDS epidemic are poor; within sub-Saharan Africa, however, the hardest hit countries are relatively richer.

Despite the lack of evidence, poverty is still believed to be a driver of the epidemic. A number of compelling arguments have been made that would support the notion that poverty causes AIDS. A naive reason underpinning this view is that health and disease exposure are usually positively correlated with poverty: richer people live longer, are in better health, and are less exposed to the deadliest diseases in low-income countries (diarrheal diseases, malaria, and so forth). This argument does not work in the case of HIV/AIDS, because the HIV virus is contracted very differently from other contagious diseases. Indeed, it is associated with behaviors and characteristics that are often associated with higher income, such as more concurrent partners, geographic mobility, and urbanization. One study characterizes these traits as those that are a direct function of wealth (e.g., increased demand for partners) and those that are correlated with wealth (such as residence and population density).

Another study examines empirically if higher household incomes are associated with less risky behaviors for individuals (particularly females) in Cape Town, South Africa. Females in poorer households are more likely to be sexually active and experience earlier sexual debut. They are more likely to reduce condom use when they experience economic shocks, but are less likely to have multiple partners. Males are more likely to have multiple partners when confronted with a negative economic shock. However, overall, the study does not find systematic difference in condom use at last sex by income level or the experience of economic shocks.

Education

There have been different conclusions reached about the association between HIV infection and education. There are various reasons why the association may be different, including the specific context and ways of analyzing the data but the factor that seems to have the biggest influence is the time the data was recorded relative to the stage of the HIV/AIDS epidemic in the country.

Several researchers completed two systematic reviews of studies relating to the association between educational attainment and risk of HIV infection in sub-Saharan Africa. The first review concluded that there was either no association between educational attainment and HIV infection (16 studies) or that there was a positive association between education and HIV infection (15 studies), with the exception of one case of negative association in Uganda where the response to the epidemic was the most developed.

An updated version of the review combined additional data published between 2001 and 2006 with the previous data. Overall, 44 studies did not show any statistically significant association between HIV infection and education, 20 studies showed a positive association, and in only 8 studies was there a negative association. In this updated version, there is evidence that the HIV epidemic is changing as shown by the fact that a larger proportion of studies conducted from 1996 onwards identified a lower risk of infection associated with the most educated than studies from before 1996; 7 studies showed a negative association with post-1996 data compared with only one study showing a negative association with the pre-1996 data. In addition, studies from after 1996 (5/40 studies) were less likely to show a positive association between HIV infection and the highest level of education than studies from before 1996 (15/32 studies). In studies from 1996 onwards that showed changes over time, there seemed to be a shift from strong positive associations toward weaker or negative associations between the highest levels of educational attainment and HIV infection. Additionally, HIV prevalence seemed to fall more consistently among the higher educated groups. Another study also noted a shift toward a more negative association between HIV and education between 1995 and 2003 based on the analysis, controlling for wealth, of data from serial population-based surveys in both urban and rural Zambia.

Referring to the two systematic reviews above, some researchers highlight the theory that the nature of the relationship between education and HIV infection is changing over time, whereby the early positive association between education and HIV is weakening as the epidemic matures in a particular country, though they also say that there is no hard evidence that these shifting associations can be attributed to a causal effect of education on HIV infection rates.

It was also found that there is a negative association between HIV and education among young women in an analysis of an individual-level longitudinal dataset in rural Uganda. It explores the evolution of this association over a period of 12 years and finds it changes over time. The study found no robust association between HIV/AIDS and education in 1990 but then found a negative association for young females in 2000.

Occupation

Occupation can also contribute to the risk of HIV infection and transmission. Commercial sex workers have been identified as a particularly vulnerable group. One study uses a panel set of 192 self-reported daily diaries compiled by commercial sex workers in Kenya to analyze decisions to engage in unprotected sex with clients. It finds that women who engage in transactional sex substantially increase their supply of risky, better compensated sex to cope with unexpected health shocks, particularly the illness of another household member. Women are 3.1% more likely to see a client, 21.2% more likely to have anal sex, and 19.1% more likely to engage in unprotected sex on days in which another household member (typically a child) falls ill. Similar responses are observed on days just after a woman recovers from the symptoms of a sexually transmitted infection (STI), which arguably might be seen as an exogenous shock to her ability to supply sex, or from other health problems. Women do this in order to capture the roughly 42 Kenyan shilling (US$0.60) premium for unprotected sex and the 77 shilling (US$1.10) premium for anal sex. Other studies, in very different settings, Calcutta and Mexico respectively, confirms the existence of a compensating differential and that female sex workers not using condoms obtain higher prices.

Truck drivers, migrants, and miners are also often perceived as occupations at risk. Two researchers investigate the role that mines and migration played in southern Africa. They start from the observation that Swaziland and Lesotho are the countries with the highest HIV prevalence in the world. They have in common another distinguishing feature: during the past century they sent massive numbers of migrant workers into South African mines. A job in the mines implies spending a long period away from the household of origin surrounded by an active sex industry. This creates potential incentives for multiple concurrent partnerships. Using DHS, their analysis shows that migrant miners aged 30–44 years are 15% points more likely to be HIV positive and having a migrant miner as a partner increases the probability of infection for women by 8% points. The study also shows that miners are less likely to abstain and to use condoms and that female partners of miners are more likely to engage in extramarital sex. The fact that mobility might be one of the key factors of HIV transmission is also highlighted by another study that shows a positive relationship between HIV prevalence and the volume of exportations. However, a recent study examining the effects of the early twenty-first century copper boom on risky sexual behavior in Zambian copper mining cities found that the copper boom substantially reduced rates of transactional sex and multiple partnerships in copper mining cities. Copper boom induced in-migration to mining cities appears to have contributed to these reductions.

 (Micro-) Economic Consequences Of HIV/AIDS

From a microeconomic point of view, the costs of the epidemic are numerous. The negative impact on labor markets has been documented. For example, using firm-level data from South Africa and Botswana, one study calculates that the value of an incident HIV infection was between 0.5 and 3.6 times the annual salary of the worker. It estimated that costs varied widely between firms and among job levels within the firm. Another studied the productivity and attendance of 54 tea workers who died or were medically retired because of AIDS between 1997 and 2002 compared with other workers. After adjusting for age and environmental factors, cases were absent from work 31 days or more often (an increase of 87%); spend 22 days more on light duty (an increase of 66%); produce an average of 7.1 kg less tea leaf per plucking day (a decrease of 17%), when compared with the control group.

One of the most devastating consequences of the HIV/AIDS epidemic is the large increase in the number of orphans. In 2008, more than 14.1 million children in sub-Saharan Africa were estimated to have lost one or both parents to AIDS. There is a large literature on the consequences of orphanhood. Summarizing it has been done elsewhere and would be beyond the scope of this article. In brief, though the results from cross-sectional studies point to a large heterogeneity in the orphan/nonorphan differential across countries, longitudinal studies who can contrast the situation of the child before and after the death of the adult generally conclude that orphans are disadvantaged in terms of schooling outcomes, even if it is not always in terms of enrollment.

Beyond orphanhood, the HIV epidemic could reduce the incentives to invest in education and affect fertility behaviors. By looking at the DHS data from 15 countries in sub-Saharan Africa, one study examines the relationship between HIV prevalence and changes in human capital investment over time and finds that areas with higher HIV prevalence experienced relatively larger declines in schooling. One of the suggested mechanisms is that a lower life expectancy reduces the incentives to invest in human capital. Another also finds that short life-spans might be one of the reasons why, even when confronted with high HIV prevalence numbers, the extent of behavior change has been limited in most African settings.

Yet another study shows evidence for the fact that HIV has had little impact on fertility, both overall and in a sample of HIV-negative women; however, it was estimated that the presence of HIV reduces the average number of births a woman gives during her lifecycle by 0.15.

HIV Prevention

Although this article focuses on the economic and behavioral aspects of the HIV/AIDS epidemic, it is worth noting that currently the field of HIV prevention is dominated by recent advances in biomedical interventions for HIV prevention. This section starts by reviewing some of these advances, with some emphasis on the behavioral responses to these advances. The discussion moves next to behavioral interventions for HIV prevention.

Biomedical Interventions

The first biomedical approach to be rigorously tested for HIV was the treatment of other STIs. As summarized in one particular study, the earliest study of the efficacy of treating other STIs on HIV incidence conducted in Tanzania suggested that when STIs are treated, HIV infection declined by almost 40% over a 2 year period. Following this result, STI treatment was included in the catalog of HIV prevention measures endorsed by the World Health Organization (WHO) and UNAIDS. However, another randomized control trial in Uganda showed contradictory results and other studies have not replicated the level of efficacy found in the initial study.

However, male circumcision has been shown to be protective and more recently, new biomedical approaches have been more successful. In particular, ‘treatment for prevention’ or ‘test-and-treat,’ and preexposure chemoprophylaxis for HIV prevention have shown promising results.

Male Circumcision

The evidence showing the protective effect of male circumcision from three randomized control trials is strong. Unlike other HIV prevention strategies, male circumcision is a onetime procedure with lifelong benefits and thus potentially highly cost effective. However, till date, there is no rigorous impact evaluation of male circumcision at scale. Those would be important studies to carry not only to confirm the external validity of the randomized control trials but also to learn what are the most effective delivery mechanisms for scaling up male circumcision or to assess whether behavioral responses such as disinhibition might differ in an environment where the benefits of male circumcision have been largely publicized and where a large number of men have been recently circumcised.

Treatment For Prevention

The ‘treatment for prevention’ approach proposes to test regularly a large fraction of the population and treat immediately those who have tested positive with antiretroviral therapies, without waiting for the AIDS symptoms to develop. By treating HIV positives immediately after they have tested, the objective is to reduce the viral load of HIV positives and therefore their infectiousness. While earlier studies advocating this approach were based on modeling, recent results from the HPTN 052 study indicate that treatment for prevention is efficacious.

Preexposure Chemoprophylaxis For HIV Prevention

One study also reports on recent trials evaluating preexposure chemoprophylaxis for HIV prevention. In the Center for the AIDS Programme of Research in South Africa (CAPRISA) study in South Africa, high-risk women used an applicator that delivered 1% tenofovir gel into the vaginal vault up to 12 h before, and within 12 h after intercourse. Investigators reported a 39% reduction in overall acquisition of HIV, and the maximum reduction was 54% among the most adherent women. In the Iniciativa Profilaxis Pre Exposicion or Prexposure Prophylaxis Initiative (iPrEx) study in 2010, HIVnegative men who have sex with men were given daily an antiretroviral combination, emtricitabine and tenofovir disoproxil fumarate (TDF plus FTC) for up to 2.8 years. The study recorded a 44% reduction in HIV acquisition and, as with the CAPRISA study, efficacy was strongly associated with concentrations of antiretroviral drugs, a direct marker of adherence. By contrast, the Preexposure Prophylaxis Trial for HIV Prevention among African Women (FEM-PrEP) trial of TDF plus FTC offered to high-risk women was discontinued because an equal number of infections occurred in both the placebo and treatment groups.

As with treatment for prevention, the efficacy and efficiency of preexposure chemoprophylaxis for HIV patients needs to be further established and confirmed, but if they are confirmed it would open very promising perspectives for the prevention of sexual transmission. Compared with treatment as prevention, preexposure chemoprophylaxis offers two advantages. First, there is no need for frequent and widespread testing in order to identify HIV-positive individuals. This is logistically challenging in most settings in sub-Saharan Africa, especially if one of the objectives is to detect individuals with recent HIV infections that are more infectious, but more difficult to detect with accuracy. Second, preexposure chemoprophylaxis for HIV prevention can be self-targeted by individuals who feel they are most at risk. However, both approaches require a high level of adherence in the absence of symptoms and are operationally challenging to implement considering that it has proved difficult so far to fully scale up HIV testing in the general population and access to antiretroviral treatment for all AIDS patients.

Behavioral Interventions

One study reviews 37 randomized controlled trials of HIV prevention interventions and finds only six demonstrating effects in reducing HIV incidence. Those six were all evaluating biomedical interventions (male circumcision trials, STI treatment, and care). None of the behavioral interventions reviewed demonstrated impact in reducing HIV incidence. The review suggests that lack of statistical power, poor adherence, and diluted versions of the intervention in comparison groups may have been important issues in some of the trials that did not show any results.

Information And Education Campaigns

IECs have been among the first behavioral interventions for HIV prevention. One researcher reviews the much touted abstain, be faithful, use condoms (ABC) campaigns in Uganda. The study concludes that the effects of such a national mass media campaign on behavior are difficult to estimate as a control group is not available. The ABC initiative in Uganda, combined with a high level of political commitment to HIV prevention, seemed to have been successful in significantly reducing the prevalence of HIV. However in mass efforts such as this, it is difficult to ascribe success to individual components (there is a debate about the relative importance of condoms in the ABC strategy), but they do provide suggestive evidence that broad-based and well supported efforts at behavior change can be effective prevention strategies. Overall, IECs by itself have not been shown to have more than a minor impact on patterns of HIV transmission and the trajectory of the epidemic. Numerous studies have shown that information alone is typically insufficient to change risk behavior. The impact of mass media campaigns tends to be short in the absence of an ongoing effort, and these campaigns can be aided by condom distribution and by more targeted education programs aimed at youth in and out of school.

HIV Testing And Counseling

HTC is recognized as the necessary gateway for HIV/AIDS treatment. However, the prevention benefits of individual HTC remain under discussion. One study estimates the behavioral responses by individuals to a public HIV testing program. It posits that only individuals who are surprised by the test results, i.e., low-risk individuals testing HIV positive or high-risk individuals testing negative, will change their behaviors. For those individuals HTC can lead to unexpected behaviors that might not reinforce prevention. It finds that although the aggregate effect of the testing program is quite small, the effects disaggregated by private beliefs about own risks are consistent with information elastic behavior for the average individual. It concludes that the subgroups of the population affected by HTC may have roughly offsetting behavioral responses, which may lead to little effect or possibly even perverse outcomes with regard to an objective of lowering disease transmission.

Another study finds that beliefs are an important determinant of risky behavior, with downward revisions in the belief of being HIV positive increasing risky behavior and upward revisions decreasing it. Yet another tests the hypothesis that only individuals who are surprised by the test results will change their behaviors, using STIs as objectively measured proxies for unsafe sexual behavior. On the one hand, individuals who believed they were at low risk for HIV before testing, are nine times more likely to contract an STI following an HIV-positive test, indicating riskier sexual behavior. On the other hand, individuals who believed they were at high risk for HIV have an 84% decrease in their likelihood of contracting an STI following an HIV-negative test, indicating safer sexual behavior. When HIV tests agree with a person’s belief of HIV infection, there is no statistically significant change in contracting an STI. Using the randomly assigned incentives and distance from results centers as instruments for the knowledge of HIV status, one researcher finds that sexually active HIV-positive individuals who learned their results are 3 times more likely to purchase condoms 2 months later than sexually active HIV-positive individuals who did not learn their results. However, there is no significant effect of learning HIV-negative status on the purchase of condoms.

Meta-analyses of the prevention benefits of HTC conclude that HIV counseling and testing appears to provide an effective means of secondary prevention for HIV-positive individuals but is not an effective primary prevention strategy for uninfected participants and that, overall, there is only moderate evidence in support of HTC as an effective prevention strategy.

Joint couple or partner testing appears to have stronger prevention benefits, especially in the case of serodiscordant couples. However, despite the importance of couple testing for treatment and prevention, there are few successful experiences of HTC programs reaching couples. Recent evidence on the effectiveness of ART for the prevention of HIV transmission among couples makes this a key intervention of prevention programs in generalized epidemic countries. Recent evidence from Rwanda suggests that pay-for-performance schemes at the health facility level can be an effective intervention to target discordant couples for HTC.

School-Based Interventions

The school environment offers a useful platform to deliver HIV information and prevention messages to individuals just before or as they start their sexual life.

Several researchers analyzed results from a randomized evaluation comparing two different HIV prevention interventions and one economic intervention, and their impact on the students in certain behaviors considered to be risk factors for HIV infection. They tested three different types of school based interventions in rural Kenya. One intervention involved training teachers in the national HIV/AIDS curriculum for them to present to their students. The second intervention consisted of students being encouraged to debate the benefits of using condoms and write essays on ways to protect themselves against HIV. The third intervention involved lowering the cost of schooling by providing school uniforms to students attending school as a way to get students to stay in school longer. To measure effectiveness, the researchers primarily evaluated teenage childbearing as a proxy for unprotected sex, the main risk factor for HIV/AIDS in Africa. They also collected information on knowledge, attitudes, and behavior regarding HIV/AIDS. The teacher training was found to have little impact on teen childbearing, students’ knowledge, and self-reported sexual activity and condom use. The debate and essay intervention increased self-reported condom use, but not self-reported sexual activity. Paying for uniforms reduced dropout rates by 15%, resulted in an almost 10% decrease in teen childbearing, girls were 12% less likely to be married, and boys were 40% less likely to be married.

The UK Department for International Development (DFID) trial (2004) in rural Tanzania evaluated the impact of an intervention aimed at changing the knowledge and sexual behavior of adolescents on HIV rates, other STIs, unintended pregnancy and adolescents’ knowledge, and reported attitudes and behaviors. The intervention included an in-school teacher-led, peer-assisted sexual and reproductive health education component, training for health workers to make reproductive health services at the clinics more youth-friendly, community-based condom promotion, and periodic community activities promoting sexual health. Comparing the communities that received the interventions with the control communities showed that the intervention communities had statistically significant improvement in knowledge and reported sexual attitudes for both males and females. Males also reported delayed sexual debut, fewer sexual partners, and more condom use at last sex. However, there was no evidence of a consistent impact of the intervention on biological outcomes including HIV incidence, other STIs, and unintended pregnancies.

A review of 11 quasiexperimental designs that measured the impact of a variety of school-based HIV prevention interventions in sub-Saharan Africa reinforce the finding from the DFID trial that behavior is more difficult to change than knowledge.

Although general HIV knowledge may not often result in behavior change, another study shows that specific information that distinguishes the levels of HIV risk may be more useful in changing behavior. The study rigorously tests an information campaign telling teenagers about the relative risks of different types of partners, based on their HIV infection rates. The objective of the campaign was to make teenagers aware of the relative risks of partners of different ages in the hope that they will take these different levels of risk into account when choosing a partner. As a result of the campaign, the incidence of cross-generational pregnancies among the treatment group decreased by 61% while intragenerational pregnancies remained stable. This information on the relative risks of different partners resulted in a sizable decrease in unprotected sex between older men and teenage girls but without an increase in unprotected sex between teenage boys and girls. In contrast, another program that only gave general information about HIV risk had no impact on the incidence of unprotected sex as measured by pregnancy rates.

Conditional Cash Transfers

Conditional cash transfer programs have become an increasingly popular approach for incentivizing socially desirable behavioral change. The principle of conditionality – making payments contingent, for example, on a minimal level of schooling attendance or preventative care use – distinguishes conditional cash transfer programs from more traditional means-tested social programs. The evaluation of conditional cash transfer programs have shown that they can be effective at raising consumption, education, and preventative health care, as well as actual health outcomes. Similarly, ‘contingency management’ approaches have shown important substance abuse reductions by conditioning rewards on negative tests for drug or alcohol. The evidence on the efficacy of conditional cash transfers for STI or HIV prevention is still unfolding and remains limited. In Malawi, small financial incentives have been shown to increase the uptake of HTC. Another study in Malawi, conducted a conditional cash transfer program for adolescents in which the cash transfer was conditional on school attendance but which, in addition to increased enrollment and attendance also caused a reduction in HIV and herpes simplex virus type 2 (HSV-2) incidence. HIV prevalence among program beneficiaries was 60% lower than the control group (1.2% vs. 3%). Similarly, the prevalence of HSV-2 (which is the common cause of genital herpes) was more than 75% lower in the combined treatment group (0.7% vs. 3%). No significant differences were detected between those offered conditional and unconditional payments. In addition, cash payments offered to the girls who had already dropped out of school at the beginning of the trial made no difference on their risk of HIV or HSV-2 infection. The same program also led to a modification of self-reported sexual behaviors with adolescent girls having younger partners.

Till date, two studies evaluated conditional cash transfers in which the conditionality is attached to negative test results for STIs. In Malawi, one study tested an intervention promising a single cash reward in 1 years’ time for individuals who remained HIV negative. This design had no measurable effect on HIV status, but the number of seroconversions in the sample was very small and statistical power was therefore low. The Rewarding STI Prevention and Control in Tanzania (RESPECT) study evaluated a randomized intervention that used economic incentives to reduce risky sexual behavior among young people aged 18–30 years and their spouses in rural Tanzania. The goal was to prevent HIV and other STIs by linking cash rewards to negative STI test results assessed every 4 months. The study tested the hypothesis that a system of rapid feedback and positive reinforcement using cash as a primary incentive to reduce risky sexual behavior could be used to promote safer sexual activity among young people who are at high risk of HIV infection. Results of the randomized controlled trial after 1 year showed a significant reduction in STI incidence in the group that was eligible for the US$20 quarterly payments, but no such reduction was found for the group receiving the US$10 quarterly payments. Further, though the impact of the Conditional Cash Transfers (CCTs) did not differ between males and females, the impact was larger among poorer households and in rural areas. Although the results from those studies are important in showing that the idea of using financial incentives can be a useful tool for preventing HIV/STI transmission, this approach would need to be replicated elsewhere and implemented on a larger scale before it could be concluded that such conditional cash transfer programs, for which administrative and laboratory capacity requirements are significant, offer an efficient, scalable, and sustainable HIV prevention strategy.

AIDS Treatment

Antiretroviral therapy (ART) has dramatically reduced morbidity and mortality for people living with HIV/AIDS. By the end of 2010, an estimated 6.6 million people in low and middle-income countries received ART. In sub-Saharan Africa, approximately 47% of the 14.2 million eligible people living with HIV were on ART. This is an extraordinary achievement, considering that as recently as 2003, relatively few people living with HIV/AIDS had access to ART in Africa. A total of 2.5 million deaths have been averted in low and middle-income countries since 1995 due to the ART being introduced, according to new calculations by UNAIDS.

Adherence To Treatment

Medical research has established that a minimum level of adherence to antiretroviral drug (ARV) treatment of 95% is necessary to achieve significantly better health outcomes as assessed by the viral load, immune system, and occurrence of opportunistic infections. Nonadherence predicts disease progressions and survival rates, and increases the risk of transmission of drug-resistant viruses. Failure to achieve proper adherence to treatment is thus both an individual and collective risk.

Determinants of adherence depends on several factors such as the treatment regimen (which can be quite complex and include food restrictions, specific schedules, etc.), disease characteristics, the quality of the patient–provider relationship, or the clinical setting. Sociodemographic factors do not consistently predict adherence behavior. The meta-analysis on socioeconomic status as a determinant of adherence finds that while the relationship is weak, there is generally a positive association between income, education, or employment status and adherence. It is worth noting that adherence is not found to be consistently lower in developing countries, and largely depends on access to treatment and financial barriers. When therapy is fully subsidized in developing countries, it can be at least as good as in developed countries.

Even when treatment per se is free, transportation costs to the health facility to get a prescription refilled are found to be a powerful barrier to adherence. Moreover, patients have to make ‘impossible choices’ between competing claims: transport costs and good nutrition of the patients compete with schooling fees or medical costs for children, food for the rest of the family, etc. As already mentioned, malnutrition can be an obstacle to adherence.

Several interventions aiming to improve adherence have been evaluated. For example, weekly Short Message Service (SMS) reminders have been shown to increase the percentage of participants achieving 90% adherence to ART by approximately 13–16% compared with no reminder and were also effective at reducing the frequency of treatment interruptions.

The Economic Benefits Of Antiretroviral Treatment

The most immediate benefit of the scaling up of antiretroviral treatment is a reduction in mortality and morbidity. A secondorder set of benefits is related to the increase of labor supply and productivity of AIDS patients and their family members as well as related changes in income, time allocation, and school participation of children.

A study from Botswana provides evidence on the link between a worker’s health status (measured by his/her cluster of differentiation 4 (CD4) count) and absenteeism in a given month, using measurements of the CD4 count at 0, 6, and 12 months after treatment initiation. The estimates provide robust evidence of an inverse V-shaped pattern in worker absenteeism around the time of ARV treatment inception. In the 1–5 years before the start of treatment, there is no difference in the rate of worker absenteeism before the start of treatment. At 12–15 months before the start of treatment, there is a sharp increase in absenteeism to approximately 20 days in the year before the start of treatment and a peak of 5 days in the month of treatment initiation (absence rate of 22%). Recovery is quick within the first year. At 1–4 years after treatment starts, treated workers have low rates of absenteeism similar to nontreated workers. In Tamil Nadu, India, at 6 months after initiation of ART, AIDS patients were 10% points more likely to be economically active and worked 5.5 additional hours per week.

On the basis of data from rural Kenya, several researchers compare the change in the extensive and intensive margins of labor supply of patients on ARV and their household members. They document a 20% increase in the likelihood of patient participating in labor force and a 35% increase (7.9 h) in weekly hours worked within 6 months of treatment. Young boys in treated patients’ households work significantly less after treatment initiation, whereas girls and adult household members do not change their labor supply. In the same setting in Kenya, with ARV treatment, females increase time for water and firewood collection, but decrease time on medical care translating into a lower burden on children with less time spent on housework and chores. Finally, based on the same longitudinal survey data from Kenya, weekly hours of school attendance of children, particularly for girls, in the patient’s household increased by more than 20% within 6 months after ARV treatment was initiated for the adult patient. In Kenya, there is weaker evidence that the short-term nutritional status of young children also improves. However, in a recent study in Zambia, the researcher finds that adult access to ART resulted in increased weight-for-age and decreased incidence of stunting among children younger than 60 months of age.

At The Intersection Of Prevention And Treatment: Disinhibition Behaviors

Part of the economics literature on HIV/AIDS has investigated disinhibition – or risk compensation – behaviors. The main proposition of this literature is that people may alter their behavior in response to perceived changes in risk. In the specific case of HIV/AIDS, the focus has been mainly related to the increased access to antiretroviral treatment. The concern is that increased access to ART may lead to a decrease in the perceived risk and costs of contracting HIV and, as a consequence, may lead to an increase of risky sexual behaviors. Such disinhibition behaviors, if large enough, may (at least partially) offset the benefits of scaling up access to ART. This conjecture is supported by several studies in the US and Europe, which have identified an upward trend in risky sexual behaviors since the introduction of ART in 1996. More specifically, an association has been identified between decreased concern about HIV due to ART availability and unprotected sex, and in particular among men who have sex with men.

Investigations of disinhibition behaviors in sub-Saharan Africa are limited. Studies exploring directly the behaviors of ART patients have generally concluded that there was no evidence of increase in risky behaviors after the ART initiation, even if sexual activity increased. One of the earliest studies looked at change in the use of condom by sex workers in Nairobi, Kenya. This analysis provided at least some suggestive evidence that condom use by sex workers decreased when ‘fake’ cures of AIDS were announced. Such a pattern is consistent with disinhibition behaviors, although the result may not be generalizable to the general population as it uses a much selected segment of the population. Another study used population-based surveys to test risk compensation behavior in the general population in a sub-Saharan African context. The researchers observed that in Kisumu (Kenya), ART-related risk compensation and the belief that ART cures HIV were associated with an increased HIV seroprevalence in men but not women. Others study the effect of increased access to ART on self-reported risky sexual behavior, using the data collected in Mozambique in 2007 and 2008. Controlling for unobserved individual characteristics, the findings support the hypothesis of disinhibition behaviors. In particular, risky behaviors are more positively associated with efficacious ART for family members of HIV-positive persons and for individuals from neighboring households, whereas disinhibition behaviors are not found among AIDS patients themselves.

Although disinhibition might more directly be a consequence of the availability of ART, disinhibition behaviors could also be present as a consequence of HIV prevention interventions. For example, one study advances that HTC might be effective in persuading HIV-positive individuals to reduce their risky behaviors and the risk of transmission of HIV to their partners, but potentially leads to disinhibition among those who receive an HIV-negative test result. Disinhibition should be considered and investigated in the case of male circumcision, treatment for prevention, and preexposure prophylaxis. In the case of male circumcision, it is possible that as a consequence of male circumcision – which is protective, but only to a certain extent – male individuals and their partners opt for less safe sexual practices and, for example, become less likely to use condoms or more likely to engage in concurrent partnerships. Another study discusses compensating behaviors related to male circumcision. The assessment is that the current empirical evidence does suggest that disinhibition is unlikely to substantially reduce the effectiveness of medical male circumcision. This assessment is based on the evidence from self-reported sexual behaviors of study participants in the randomized control trials that have established the efficacy of medical male circumcision. It would be important to assess the possibility of disinhibition from male circumcision interventions at scale.

Overall, it is fair to conclude that the evidence on disinhibition behaviors is limited and inconclusive. Several studies have provided a comprehensive review, with studies finding evidence of disinhibition and others not. The evidence is even more limited in sub-Saharan Africa but the potential risks associated with disinhibition on a large scale are important enough to be taken into consideration in further studies.

Conclusion

After reviewing the behavioral and socioeconomic determinants of HIV transmission, this article has focused on HIV prevention intervention and AIDS treatment. There is a tendency to present prevention and treatment as alternatives competing for scarce (donor) resources. However, HIV prevention remains crucial. Only by sustaining recent reductions in mortality and bringing down the number of new infections will the total number of people with HIV finally decline and will an AIDS transition be attainable.

It has been stressed that behavioral responses are very important mediators of HIV transmission and of the efficacy of HIV prevention and AIDS treatment. Currently, the field of HIV prevention is dominated by recent advances in biomedical interventions for HIV prevention such as male circumcision, treatment for prevention, and preexposure chemoprophylaxis. Though these interventions represent important breakthroughs, it is important to keep in mind potential behavioral responses, such as disinhibition to these interventions as well as the role that incentives can play. Further, it will be important to evaluate those interventions at scale. Such impact evaluations would not only confirm the external validity of the randomized control trials but also would allow learning what are the most effective delivery mechanisms for scaling up those interventions.

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Health Services in Low- and Middle-Income Countries
Internal Geographical Imbalances