A community trial of the impact of improved sexually transmitted disease treatment on the HIV epidemic in rural Tanzania: 1. Design

Assessment of vaccine herd protection in a cluster-randomised trial of Vi conjugate vaccine against typhoid fever: results of further analysis

Background

A cluster-randomised trial of Vi-tetanus toxoid (Vi-TT) conjugate vaccine conducted in urban Bangladeshi children found a high level of direct protection by Vi-TT but no significant vaccine herd protection. We reassessed the trial using a "fried egg" analysis to evaluate whether herd protection might have been obscured by transmission of typhoid into the clusters from the outside.

Methods

A participant- and observer-blind, cluster-randomised trial was conducted between February 14, 2018 and August 12, 2019 in three wards of Mirpur, a densely populated urban area of Dhaka, Bangladesh. Children 9 months to under 16 years of age in 150 geographic clusters, which had a total of 311,289 persons present at baseline or entering during follow-up, were randomised by cluster to a single-dose of Vi-TT or Japanese encephalitis (JE) vaccine. Vi-TT protection against typhoid fever, detected at 8 treatment centres serving the study population, was compared in the original clusters for the trial, and for progressively more central subclusters ("yolks" of the "fried egg") of the cluster residents. If transmission of typhoid into the clusters had diluted observed vaccine herd protection, we hypothesised that analysis of the innermost "yolks" would reveal vaccine herd protection that was not evident in analysis of the entire clusters. The trial is registered at www.isrctn.com as ISRCTN11643110.

Findings

At ≤18 months of follow-up, total vaccine effectiveness (protection of Vi-TT recipients relative to JE vaccine recipients) was 85% (95% CI: 76%, 90%); indirect effectiveness (protection of non-Vi-TT recipients in Vi-TT clusters relative to non-JE vaccine recipients in JE vaccine clusters) was 17% (95% CI: -13%, 40%); and overall effectiveness (protection of all residents in the Vi-TT clusters relative to all residents of the JE vaccine clusters) was 57% (95% CI: 44%, 66%). Analyses of subpopulations in inner 75%, 50% and 25% "yolks" of the clusters failed to reveal significant changes in any of these estimates.

Interpretation

Our analysis did not reveal Vi-TT herd protection in the trial. Consideration should be given to exploring whether targeting adults as well as children with Vi-TT yields appreciable levels of vaccine herd protection.

Funding

Bill & Melinda Gates Foundation (OPP1151153, INV-025388).

A mixed model formulation for designing cluster randomized trials with binary outcomes

Cluster randomized trials (CRTs) are unlike traditional individually randomized trials because observations within the same cluster are positively correlated and the sample size (number of clusters) is relatively small. Although formulae for sample size and power estimates of CRT designs do exist, these formulae rely upon first-order asymptotic approximations for the distribution of the average intervention effect and are inaccurate for CRTs that have a small number of clusters. These formulae also assume that the intracluster correlation (ICC) is the same for each cluster in the CRT. However, for CRTs in which the clusters are classrooms or medical practices, the degree of ICC is often a factor of how many students are in each classroom or how many patients are in each practice. Specifically, smaller clusters are expected to have larger ICC than larger clusters. A weighted sum of the cluster means, D, is the statistic often used to estimate the average intervention effect in a CRT. Therefore, we propose that a saddlepoint approximation is a natural choice to approximate the distributions of the cluster means more precisely than a standard large-sample approximation. We parameterize the ICC for each cluster as a random effect with a predefined prior distribution that is dependent upon the size of each cluster. After integrating over the range of the random effect, we use Monte Carlo methods to generate sample cluster means, which are in turn used to approximate the distribution of D with saddlepoint methods. Through numerical examples and an actual application, we show that our method has accuracy that is equal to or better than that of existing methods. Futhermore, our method accommodates CRTs in which the correlation within cluster is expected to diminish with the cluster size.

Evaluating Public Health Interventions: 2. Stepping Up to Routine Public Health Evaluation With the Stepped Wedge Design

In a stepped wedge design (SWD), an intervention is rolled out in a staggered manner over time, in groups of experimental units, so that by the end, all units experience the intervention. For example, in the MaxART study, the date at which to offer universal antiretroviral therapy to otherwise ineligible clients is being randomly assigned in nine "steps" of four months duration so that after three years, all 14 facilities in northern and central Swaziland will be offering early treatment. In the common alternative, the cluster randomized trial (CRT), experimental units are randomly allocated on a single common start date to the interventions to be compared. Often, the SWD is more feasible than the CRT, both for practical and ethical reasons, but takes longer to complete. The SWD permits both within- and between- unit comparisons, while the CRT only allows between-unit comparisons. Thus, confounding bias with respect to time-invariant factors tends to be lower in an SWD than a CRT, but the SWD cannot as readily control for confounding by time-varying factors. SWDs have generally more statistical power than CRTs, especially as the intraunit correlation and the number of participants within unit increases. Software for both designs are available, although for a more limited set of SWD scenarios.

Bacterial Vaginosis and Subclinical Markers of Genital Tract Inflammation and Mucosal Immunity

Bacterial vaginosis (BV) has been linked to an increased risk of human immunodeficiency virus (HIV) acquisition and transmission in observational studies, but the underlying biological mechanisms are unknown. We measured biomarkers of subclinical vaginal inflammation, endogenous antimicrobial activity, and vaginal flora in women with BV and repeated sampling 1 week and 1 month after completion of metronidazole therapy. We also compared this cohort of women with BV to a healthy control cohort without BV. A longitudinal, open label study of 33 women with a Nugent score of 4 or higher was conducted. All women had genital swabs, cervicovaginal lavage (CVL) fluid, and cervicovaginal biopsies obtained at enrollment and received 7 days of metronidazole treatment. Repeat sampling was performed approximately 1 week and 1 month after completion of therapy. Participant's baseline samples were compared to a healthy, racially matched control group (n=13) without BV. The CVL from women with resolved BV (Nugent 0-3) had significantly higher anti-HIV activity, secretory leukocyte protease inhibitor (SLPI), and growth-related oncogene alpha (GRO-α) levels and their ectocervical tissues had significantly more CD8 cells in the epithelium. Women with persistent BV after treatment had significantly higher levels of interleukin-1β, tumor necrosis factor alpha (TNF-α), and intercellular adhesion molecule 1 (ICAM-1) in the CVL. At study entry, participants had significantly greater numbers of CCR5(+) immune cells and a higher CD4/CD8 ratio in ectocervical tissues prior to metronidazole treatment, compared to a racially matched cohort of women with a Nugent score of 0-3. These data indicate that BV is associated with changes in select soluble immune mediators, an increase in HIV target cells, and a reduction in endogenous antimicrobial activity, which may contribute to the increased risk of HIV acquisition.

Current perspectives in HIV post-exposure prophylaxis

The incidence of human immunodeficiency virus (HIV) infection continues to rise among core groups and efforts to reduce the numbers of new infections are being redoubled. Post-exposure prophylaxis (PEP) is the use of short-term antiretroviral therapy (ART) to reduce the risk of acquisition of HIV infection following exposure. Current guidelines recommend a 28-day course of ART within 36-72 hours of exposure to HIV. As long as individuals continue to be exposed to HIV there will be a role for PEP in the foreseeable future. Nonoccupational PEP, the vast majority of which is for sexual exposure (PEPSE), has a significant role to play in HIV prevention efforts. Awareness of PEP and its availability for both clinicians and those who are eligible to receive it are crucial to ensure that PEP is used to its full potential in any HIV prevention strategy. In this review, we provide current evidence for the use of PEPSE, assessment of the risk of HIV transmission, indications for PEP, drug regimens, and management of patients started on PEP. We summarize national and international guidelines for the use of PEPSE. We explore the place of PEP within the wider strategy of reducing HIV incidence rates in the era of treatment as prevention and pre-exposure prophylaxis. We also consider the implications of recent data from interventional and observational studies demonstrating significant reductions in the risk of HIV transmission within a serodiscordant relationship if the HIV-positive partner is taking effective ART upon PEP guidelines.

Treatment as prevention: preparing the way

Potent antiretroviral therapy (ART) reduces mortality and morbidity in people living with HIV by reducing viral load and allowing their immune systems to recover. The reduction in viral load soon after starting ART has led to the hypothesis that early and widespread ART could prevent onward transmission and therefore eliminate the HIV epidemic in the long term. While several authors have argued that it is feasible to use HIV treatment as prevention (TasP), provided treatment is started sufficiently early, others have reasonably drawn attention to the many operational difficulties that will need to be overcome if the strategy is to succeed in reducing HIV transmission. Furthermore, international public health policy must be based on more than theoretical studies, no matter how appealing. Community randomized controlled trials provide the gold standard for testing the extent to which early treatment reduces incidence, but much still needs to be understood and the immediate need is for operational studies to explore the practical feasibility of this approach. Here, we examine some of the issues to be addressed, the obstacles to be overcome, and strategies that may be necessary if TasP is to be effective. Studies of this kind will provide valuable information for the design of large-scale trials, as well as essential information that will be needed if early treatment is to be incorporated into public health policy.

Population-based biomedical sexually transmitted infection control interventions for reducing HIV infection

BACKGROUND

The transmission of sexually transmitted infections (STIs) is closely related to the sexual transmission of human immunodeficiency virus (HIV). Similar risk behaviours, such as frequent unprotected intercourse with different partners, place people at high risk of HIV and STIs, and there is clear evidence that many STIs increase the likelihood of HIV transmission. STI control, especially at the population or community level, may have the potential to contribute substantially to HIV prevention.This is an update of an existing Cochrane review. The review's search methods were updated and its inclusion and exclusion criteria modified so that the focus would be on one well-defined outcome. This review now focuses explicitly on population-based biomedical interventions for STI control, with change in HIV incidence being an outcome necessary for a study's inclusion.

OBJECTIVES

To determine the impact of population-based biomedical STI interventions on the incidence of HIV infection.

SEARCH STRATEGY

We searched PubMed, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science/Social Science, PsycINFO, and Literatura Latino Americana e do Caribe em Ciências da Saúde (LILACS), for the period of 1 January1980 - 16 August 2010. We initially identified 6003 articles and abstracts. After removing 776 duplicates, one author (TH) removed an additional 3268 citations that were clearly irrelevant. Rigorously applying the inclusion criteria, three authors then independently screened the remaining 1959 citations and abstracts. Forty-six articles were chosen for full-text scrutiny by two authors. Ultimately, four studies were included in the review.We also searched the Aegis database of conference abstracts, which includes the Conference on Retroviruses and Opportunistic Infections (CROI), the International AIDS Conference (IAC), and International AIDS Society Conference on HIV Pathogenesis, Treatment and Prevention (IAS) meetings from their inception dates (1993, 1985 and 2001, respectively) through 2007. We manually searched the web sites of those conferences for more recent abstracts (up to 2010, 2010 and 2009, respectively)  In addition to searching the clinical trials registry at the US National Institutes of Health, we also used the metaRegister of Controlled Trials.We checked the reference lists of all studies identified by the above methods.

SELECTION CRITERIA

Randomised controlled trials involving one or more biomedical interventions in general populations (as opposed to occupationally or behaviourally defined groups, such as sex workers) in which the unit of randomisation was either a community or a treatment facility and in which the primary outcome was incident HIV infection. The term "community" was interpreted to include a group of villages, an arbitrary geographical division, or the catchment population of a group of health facilities.

DATA COLLECTION AND ANALYSIS

Three authors (BN, LB, TH) independently applied the inclusion criteria to potential studies, with any disagreements resolved by discussion. Trials were examined for completeness of reporting. Data were abstracted independently using a standardised abstraction form.

MAIN RESULTS

We included four trials. One trial evaluated mass treatment of all individuals in a particular community. The other three trials evaluated various combinations of improved syndromic STI management in clinics, STI counselling, and STI treatment.In the mass treatment trial in rural southwestern Uganda, after three rounds of treatment of all community members for STIs, the adjusted rate ratio (aRR) of incident HIV infection was 0.97 (95% CI 0.81 - 1.2), indicating no effect of the intervention. The three STI management intervention studies were all conducted in rural parts of Africa. One study, in northern Tanzania, showed that the incidence of HIV infection in the intervention groups (strengthened syndromic management of STIs in primary care clinics) was 1.2% compared with 1.9% in the control groups (aRR = 0.58, 95% CI 0.42 - 0.79), corresponding to a 42% reduction (95% CI 21.0% - 58.0%) in HIV incidence in the intervention group. Another study, conducted in rural southwestern Uganda, showed that the aRR of behavioural intervention and STI management compared to control on HIV incidence was 1.00 (95% CI 0.63 - 1.58). In the third STI management trial, in eastern Zimbabwe, there was no effect of the intervention on HIV incidence (aRR = 1.3, 95% CI 0.92 - 1.8). These are consistent with data from the mass treatment trial showing no intervention effect. Overall, pooling the data of the four studies showed no significant effect of any intervention (rate ratio [RR] = 0.97, 95% CI 0.78 - 1.2).Combining the mass treatment trial and one of the STI management trials, we find that there is a significant 12.0% reduction in the prevalence of syphilis for those receiving a biomedical STI intervention (RR 0.88, 95% CI 0.80 - 0.96). For gonorrhoea, we find a statistically significant 51.0% reduction in its prevalence in those receiving any of these interventions (RR 0.49, 95% CI 0.31 - 0.77). Finally, for chlamydia, we found no significant difference between any biomedical intervention and control (RR 1.03, 95% CI 0.77 - 1.4).

AUTHORS' CONCLUSIONS

We failed to confirm the hypothesis that STI control is an effective HIV prevention strategy. Improved STI treatment services were shown in one study to reduce HIV incidence in an environment characterised by an emerging HIV epidemic (low and slowly rising prevalence), where STI treatment services were poor and where STIs were highly prevalent; Incidence was not reduced in two other settings. There is no evidence for substantial benefit from a presumptive treatment intervention for all community members. There are, however, other compelling reasons why STI treatment services should be strengthened, and the available evidence suggests that when an intervention is accepted it can substantially improve quality of services provided.

A cluster randomised controlled trial of the community effectiveness of two interventions in rural Malawi to improve health care and to reduce maternal, newborn and infant mortality

BACKGROUND

The UN Millennium Development Goals call for substantial reductions in maternal and child mortality, to be achieved through reductions in morbidity and mortality during pregnancy, delivery, postpartum and early childhood. The MaiMwana Project aims to test community-based interventions that tackle maternal and child health problems through increasing awareness and local action.

METHODS/DESIGN

This study uses a two-by-two factorial cluster-randomised controlled trial design to test the impact of two interventions. The impact of a community mobilisation intervention run through women's groups, on home care, health care-seeking behaviours and maternal and infant mortality, will be tested. The impact of a volunteer-led infant feeding and care support intervention, on rates of exclusive breastfeeding, uptake of HIV-prevention services and infant mortality, will also be tested. The women's group intervention will employ local female facilitators to guide women's groups through a four-phase cycle of problem identification and prioritisation, strategy identification, implementation and evaluation. Meetings will be held monthly at village level. The infant feeding intervention will select local volunteers to provide advice and support for breastfeeding, birth preparedness, newborn care and immunisation. They will visit pregnant and new mothers in their homes five times during and after pregnancy.The unit of intervention allocation will be clusters of rural villages of 2500-4000 population. 48 clusters have been defined and randomly allocated to either women's groups only, infant feeding support only, both interventions, or no intervention. Study villages are surrounded by 'buffer areas' of non-study villages to reduce contamination between intervention and control areas. Outcome indicators will be measured through a demographic surveillance system. Primary outcomes will be maternal, infant, neonatal and perinatal mortality for the women's group intervention, and exclusive breastfeeding rates and infant mortality for the infant feeding intervention.Structured interviews will be conducted with mothers one-month and six-months after birth to collect detailed quantitative data on care practices and health-care-seeking. Further qualitative, quantitative and economic data will be collected for process and economic evaluations.

TRIAL REGISTRATION

ISRCTN06477126.

Behavioral mechanisms in HIV epidemiology and prevention: past, present, and future roles

In the 1980s, behavioral variations across geographically and socially defined populations were the central focus of AIDS research, and behavior change was seen as the primary means of controlling HIV epidemics. Today, biological mechanisms--especially other sexually transmitted infections, antiretroviral therapy, and male circumcision--predominate in HIV epidemiology and prevention. We describe several reasons for this shift in emphasis. Although the shift is understandable, we argue for a sustained focus on behavioral mechanisms in HIV research in order to realize the theoretical promise of interventions targeting the biological aspects of HIV risk. We also provide evidence to suggest that large reductions in HIV prevalence may be accomplished by small changes in behavior. Moreover, we contend that behavioral mechanisms will find their proper place in HIV epidemiology and prevention only when investigators adopt a conceptual model that treats prevalence as a determinant as well as an outcome of behavior and that explicitly recognizes the dynamic interdependence between behavior and other epidemiological and demographic parameters.

A systematic review of the quality of trials evaluating biomedical HIV prevention interventions shows that many lack power

PURPOSE

Several randomized, controlled trials (RCTs) have tested strategies to prevent sexual acquisition of HIV infection, but their quality has been variable. We aimed to identify, describe, and evaluate the quality of RCTs studying biomedical interventions to prevent HIV acquisition by sexual transmission.

METHOD

We conducted a systematic review to identify all RCTs evaluating the efficacy of biomedical HIV prevention interventions. We assessed seven generic and content-specific quality components important in HIV prevention trials, factors influencing study power, co-interventions provided, and trial ethics.

RESULTS

We identified 26 eligible RCTs. The median number of quality components judged to be in adequate or unclear was 3 (range 1-4) in 1992-1998, 3 (range 1-4) in 1999-2003, and 0 (range0-2) in 2004-2008 (p < .001). Common problems that may have biased results included low retention (median 84%), poor adherence to interventions requiring on going use (median < or =78%), and lower HIV incidence than expected a priori (in 8 of 11 trials where evaluable).

CONCLUSION

Reporting of trials of biomedical HIV prevention interventions has improved over time. However, quality improvement is needed in several key areas that influence study power, including participant retention, adherence to interventions, and estimation of expected HIV incidence.

Using participatory mapping to inform a community-randomized trial of HIV counseling and testing

Participatory mapping and transect walks were used to inform the research and intervention design and to begin building community relations in preparation for Project Accept, a community-randomized trial sponsored by the U.S. National Institute of Mental Health (NIMH). NIMH Project Accept is being conducted in five sites within four countries including Thailand, Zimbabwe, South Africa and Tanzania. Results from the mapping exercises informed decisions about the research design such as defining community boundaries, and identifying appropriate criteria for matching community pairs for the trial. The mapping also informed intervention related decisions such as where to situate the services. The participatory methods enabled each site to develop an understanding of the communities that could not have been derived from existing data or data collected through standard data collection techniques. Furthermore, the methods lay the foundation for collaborative community research partnerships.

A review of HIV/AIDS system-level interventions

The escalating HIV/AIDS epidemic worldwide demands that on-going prevention efforts be strengthened, disseminated, and scaled-up. System-level interventions refer to programs aiming to improve the functioning of an agency as well as the delivery of its services to the community. System-level interventions are a promising approach to HIV/AIDS prevention because they focus on (a) improving the agency's ability to adopt evidence-based HIV prevention and care programs; (b) develop and establish policies and procedures that maximize the sustainability of on-going prevention and care efforts; and (c) improve decision-making processes such as incorporating the needs of communities into their tailored services. We reviewed studies focusing on system-level interventions by searching multiple electronic abstracting indices, including PsycInfo, PubMed, and ProQuest. Twenty-three studies out of 624 peer-reviewed studies (published from January 1985 to February 2007) met study criteria. Most of the studies focused on strengthening agency infrastructure, while other studies included collaborative partnerships and technical assistance programs. Our findings suggest that system-level interventions are promising in strengthening HIV/AIDS prevention and treatment efforts. Based on our findings, we propose recommendations for future work in developing and evaluating system-level interventions.

An application of a modified constrained randomization process to a practice-based cluster randomized trial to improve colorectal cancer screening

BACKGROUND

When designing cluster randomized trials, it is important for researchers to be familiar with strategies to achieve valid study designs given limited resources. Constrained randomization is a technique to help ensure balance on pre-specified baseline covariates.

METHODS

The goal was to develop a randomization scheme that balanced 16 intervention and 16 control practices with respect to 7 factors that may influence improvement in study outcomes during a 4-year cluster randomized trial to improve colorectal cancer screening within a primary care practice-based research network. We used a novel approach that included simulating 30,000 randomization schemes, removing duplicates, identifying which schemes were sufficiently balanced, and randomly selecting one scheme for use in the trial. For a given factor, balance was considered achieved when the frequency of each factor's sub-classifications differed by no more than 1 between intervention and control groups. The population being studied includes approximately 32 primary care practices located in 19 states within the U.S. that care for approximately 56,000 patients at least 50 years old.

RESULTS

Of 29,782 unique simulated randomization schemes, 116 were determined to be balanced according to pre-specified criteria for all 7 baseline covariates. The final randomization scheme was randomly selected from these 116 acceptable schemes.

CONCLUSIONS

Using this technique, we were successfully able to find a randomization scheme that allocated 32 primary care practices into intervention and control groups in a way that preserved balance across 7 baseline covariates. This process may be a useful tool for ensuring covariate balance within moderately large cluster randomized trials.

Differences in HIV risk behaviors by gender in a sample of Tanzanian injection drug users

This study investigated differences in drug use and sexual behaviors among from 237 male and 123 female heroin users in Dar es Salaam, Tanzania. Multivariate models of risk of needle sharing were estimated using multivariate logistic regression. Men were significantly older, more likely to inject only white heroin, share needles, and give or lend used needles to other injectors. Women were more likely to be living on the streets, have injected brown heroin, have had sex, have had a higher number of sex partners, and have used a condom with the most recent sex partner. Being male and earning less than US $46 in the past month were significant predictors of increased risk of needle sharing. Despite differences in sociodemographic, drug use, and sexual behaviors by gender, both male and female injectors in Dar es Salaam exhibit elevated risk of HIV infection associated with drug use.

Randomization inference for balanced cluster-randomized trials

This paper discusses the choice of randomization tests for inferences from cluster-randomized trials that have been designed to ensure a balanced allocation of clusters to treatments. Methods for covariate-adjusted randomization tests are reviewed and their application to balanced cluster-randomized trials discussed. Two cluster-randomized trials with balanced designs are used to illustrate the choices that can be made in selecting a randomization test, and methods for obtaining confidence intervals for treatment effects are illustrated. The balance imposed by the randomization in these trials makes adjustment for covariates less beneficial than for an unbalanced design. However, the adjusted analyses do not appear generally to have worse properties than the unadjusted ones, and may provide protection against any imbalance that has not been controlled for in the design. The only case when adjustment for covariates may result in worse precision is when a large number of cluster-level covariates are included in the analysis. An expression is provided that allows the size of this effect to be calculated for any given set of cluster-level covariates.

Overview of Vaccine Field Studies: Types of Effects and Designs

Vaccination produces many different types of effects in individuals and in populations. The scientific and public health questions of interest determine the choice of measures of effect and study designs. Here we review some of the various measures and study designs for evaluating different effects of vaccination.

In defense of the randomized controlled trial for health promotion research

The overwhelming evidence about the role lifestyle plays in mortality, morbidity, and quality of life has pushed the young field of modern health promotion to center stage. The field is beset with intense debate about appropriate evaluation methodologies. Increasingly, randomized designs are considered inappropriate for health promotion research. We have reviewed criticisms against randomized trials that raise philosophical and practical issues, and we will show how most of these criticisms can be overcome with minor design modifications. By providing rebuttal to arguments against randomized trials, our work contributes to building a sound methodological base for health promotion research.

Can population differences explain the contrasting results of the Mwanza, Rakai, and Masaka HIV/sexually transmitted disease intervention trials?: A modeling study

OBJECTIVE

To determine whether population differences can explain the contrasting impacts on HIV observed in the Mwanza trial of sexually transmitted disease (STD) syndromic treatment (ST), the Rakai trial of STD mass treatment (MT), and the Masaka trial of information, education, and communication (IEC) with and without ST as well as to predict the effectiveness of each intervention strategy in each population.

METHODS

Stochastic modeling of the transmission of HIV and 6 STDs was used with parameters fitted to demographic, sexual behavior, and epidemiological data from the trials and general review of STD/HIV biology.

RESULTS

The baseline trial populations could be simulated by assuming higher risk behavior in Uganda compared with Mwanza in the 1980s, followed by reductions in risk behavior in Uganda preceding the trials. In line with trial observations, the projected HIV impacts were larger for the ST intervention in Mwanza than for the MT intervention in Rakai or the IEC and IEC + ST interventions in Masaka. All 4 simulated intervention strategies were more effective in reducing incidence of HIV infection in Mwanza than in either Rakai or Masaka.

CONCLUSIONS

Population differences in sexual behavior, curable STD rates, and HIV epidemic stage can explain most of the contrast in HIV impact observed between the 3 trials. This study supports the hypothesis that STD management is an effective HIV prevention strategy in populations with a high prevalence of curable STDs, particularly in an early HIV epidemic.

A community-based study to examine the effect of a youth HIV prevention intervention on young people aged 15-24 in South Africa: results of the baseline survey

OBJECTIVES

To determine whether South African youths living in communities that had either of two youth human immunodeficiency virus (HIV) prevention interventions [(a) loveLife Youth Centre or (b) loveLife National Adolescent Friendly Clinic Initiative] would have a lower prevalence of HIV, sexually transmitted infections (STIs), and high risk sexual behaviours than communities without either of these interventions.

METHODS

In 2002 the baseline survey of a quasi-experimental, community-based study was conducted in South Africa. In total 33 communities were included in three study arms (11 communities per study arm). The final sample included 8735 youths aged 15-24 years. All participants took part in a behavioural interview and were tested for HIV, gonorrhoea (Neisseria gonorrhoeae) and Chlamydia (Chlamydia trachomatis).

RESULTS

HIV prevalence was 20.0% among females and 7.5% among males (OR 3.93 95% CI 2.51-6.15). There were no significant differences between study arms for HIV, NG or CT prevalence at baseline. In multiple regression analyses, HIV was significantly associated with NG infection (OR 1.96 95% CI 1.24-3.12) but not with CT infection. Youths who reported >1 lifetime partner were also significantly more likely to be infected with HIV (OR 1.98 95% CI 1.55-2.52), as were those who reported ever having engaged in transactional sex (OR 1.86 P = 0.02) or having had genital ulcers in the past 12 months (OR 1.71 P < or = 0.001).

CONCLUSIONS

HIV prevention programmes must ensure that gender inequities that place young women at greater risk for HIV infection are urgently addressed and they must continue to emphasize the importance of reducing the number of sexual partners and STI treatment.

The cost-effectiveness of a competitive voucher scheme to reduce sexually transmitted infections in high-risk groups in Nicaragua

Current evidence suggests that sexually transmitted infection (STI) interventions can be an effective means of human immunodeficiency virus (HIV) prevention in populations at an early stage of the epidemic. However, evidence as to their cost-effectiveness when targeted at high-risk groups is lacking. This paper assesses the cost-effectiveness of a competitive voucher scheme in Managua, Nicaragua aimed at high-risk groups, who could redeem the vouchers in exchange for free STI testing and treatment, health education and condoms, compared with the status quo (no scheme). A provider perspective was adopted, defined as: the voucher agency and health care providers from the public, NGO and private sectors. The cost of the voucher scheme was estimated for a 1-year period (1999) from project accounts using the ingredients approach. Outcomes were monitored as part of ongoing project evaluation. Costs and outcomes in the absence of the scheme were modelled using project baseline data and reports, and relevant literature. The annual cost of providing comprehensive STI services through vouchers was US$62 495, compared with an estimated US$17 112 for regular service provision in the absence of the scheme. 4815 vouchers were distributed by the voucher scheme, 1543 patients were tested for STIs and 528 STIs were effectively cured in this period. In the absence of the scheme, only an estimated 85 cases would have been cured from 1396 consultations. The average cost of the voucher scheme per patient treated was US$41 and US$118 per STI effectively cured, compared with US$12 per patient treated and US$200 per STI cured in its absence. The incremental cost of curing an STI through the voucher scheme, compared with the status quo, was US$103. A voucher scheme offers an effective and efficient means of targeting and effectively curing STIs in high-risk groups, as well as encouraging quality care practices.

Determinants of the impact of sexually transmitted infection treatment on prevention of HIV infection: a synthesis of evidence from the Mwanza, Rakai, and Masaka intervention trials

Community-randomized trials in Mwanza, Tanzania, and Rakai and Masaka, Uganda, suggested that population characteristics were an important determinant of the impact of sexually transmitted infection (STI) treatment interventions on incidence of human immunodeficiency virus (HIV) infection. We performed simulation modeling of HIV and STI transmission, which confirmed that the low trial impact in Rakai and Masaka could be explained by low prevalences of curable STI resulting from lower-risk sexual behavior in Uganda. The mature HIV epidemics in Uganda, with most HIV transmission occurring outside core groups with high STI rates, also contributed to the low impact on HIV incidence. Simulated impact on HIV was much greater in Mwanza, although the observed impact was larger than predicted from STI reductions, suggesting that random error also may have played some role. Of proposed alternative explanations, increasing herpetic ulceration due to HIV-related immunosuppression contributed little to the diminishing impact of antibiotic treatment during the Ugandan epidemics. The strategy of STI treatment also was unimportant, since syndromic treatment and annual mass treatment showed similar effectiveness in simulations of each trial population. In conclusion, lower-risk behavior and the mature HIV epidemic explain the limited impact of STI treatment on HIV incidence in Uganda in the 1990s. In populations with high-risk sexual behavior and high STI rates, STIs treatment interventions may contribute substantially to prevention of HIV infection.

The effects of alternative study designs on the power of community randomized trials: evidence from three studies of human immunodeficiency virus prevention in East Africa

BACKGROUND

Randomized intervention trials in which the community is the unit of randomization are increasingly being used to evaluate the impact of public health interventions. In the design of community randomized trials (CRT), the power of the study is likely to be affected by two issues: the matching or stratification of communities, and the number and size of the communities to be randomized.

METHODS

Data from three East African community intervention trials, designed to evaluate the impact of interventions to reduce human immunodeficiency virus (HIV) incidence, are used to compare the efficiency of different trial designs.

RESULTS

Compared with an unmatched design, stratification reduced the between-community variation in the Mwanza trial (from 0.51 to 0.24) and in the Masaka trial (from 0.38 to 0.28). The reduction was smaller in the Rakai trial where the selected communities were more homogeneous (from 0.15 to 0.11). For all trials, individual matching of communities produced estimates of between-community variation similar to those from the stratified designs. The linear association between HIV prevalence and incidence was strong in the Mwanza trial (correlation coefficient R = 0.83) and the Masaka trial (R = 0.83), but weak in the Rakai trial (R = 0.28). Unmatched study designs that use smaller communities tend to increase between-community variation, but reduce the design effect and improve study power.

CONCLUSIONS

These empirical data suggest that selection of homogeneous communities, or stratification of communities prior to randomization, may improve the power of CRT.

Methods to reduce social desirability bias in sex surveys in low-development settings: experience in Zimbabwe

BACKGROUND

Social desirability bias hampers measurement of risk behavior for acquiring STDs and evaluation of control interventions. More confidential data collection methods reduce this bias in Western countries but generally require technology not available in less developed settings. GOAL The goal of this report was to describe and evaluate an informal, confidential, low-technology method-Informal Confidential Voting Interviews (ICVIs)-for collecting sexual behavior data in less developed settings.

STUDY DESIGN

Reports of multiple sex partners by sexually active, basic-literate, population-based survey participants in rural Zimbabwe randomly assigned to ICVIs and face-to-face interviews (FTFIs) were compared.

RESULTS

Ninety-two percent of respondents (n = 7,823) were sufficiently literate for ICVIs. Error rates were low but higher than in FTFIs. More male and female ICVI respondents interviewed reported multiple current sex partners (OR = 1.33 and 5.24, respectively) and multiple partners in the past month (OR = 1.71 and 2.92) and the past year (OR = 1.35 and 1.97).

CONCLUSION

The ICVI method appears to reduce bias but requires further evaluation to assess viability and effect in alternative settings.

Exploring the community response to a randomized controlled HIV/AIDS intervention trial in rural Uganda

Investigators need, both for ethical and methodological reasons, to consider the acceptability of their intervention to the study population. We explored the response to a community-based randomized controlled trial (RCT) of an HIV/AIDS behavioral change intervention in rural Uganda. The views of field-workers, trial community, nongovernment organization representatives, and religious leaders were explored via focus groups (13) and interviews (45). The results suggest that the components of the intervention valued by the community are not necessarily those prioritised by trial implementers. Specifically, prevention activities appear to be valued less than material assistance. Furthermore, universal acceptance of the trial is probably unattainable. For these reasons, sensitive mobilization, respect for community members and their appointed leaders, and ongoing communication is essential. We suggest that evaluations of process be regarded as essential to the conduct of community-based RCTs and highlight the need for appropriate evaluation indicators to facilitate this.

Incidence of HIV infection in stable sexual partnerships: a retrospective cohort study of 1802 couples in Mwanza Region, Tanzania

OBJECTIVE

To describe the dynamics of HIV transmission in stable sexual partnerships in rural Tanzania.

DESIGN

Retrospective cohort study nested within community-randomized trial to investigate the impact of a sexually transmitted disease treatment program.

METHODS

A cohort of 1802 couples was followed up for 2 years, with the HIV status of each couple assessed at baseline and follow-up.

RESULTS

At baseline, 96.7% of couples were concordant-negative, 0.9% were concordant-positive, 1.2% were discordant with the male partner being HIV-positive, and 1.2% were discordant with the female partner being HIV-positive. Individuals living with an HIV-positive partner were more likely to be HIV-positive at baseline (women: odds ratio [OR] = 75.7, 95% confidence interval [CI]: 33.4-172; men: OR = 62.4, CI: 28.5-137). Seroincidence rates in discordant couples were 10 per 100 person-years (py) and 5 per 100 py for women and men, respectively (rate ratio [RR] = 2.0, CI: 0.28-22.1). In concordant-negative couples, seroincidence rates were 0.17 per 100 py in women and 0.45 per 100 py in men (RR = 0.38, CI: 0.12-1.04). Individuals living in discordant couples were at a greatly increased risk of infection compared with individuals in concordant-negative couples (RR = 57.9, CI: 12.0-244 for women; RR = 11.0, CI: 1.2-47.5 for men).

CONCLUSION

Men were more likely than women to introduce HIV infection in concordant-negative partnerships. In discordant couples, incidence in HIV-negative women was twice as high as in men. HIV-negative individuals in discordant partnerships are at high risk of infection, and preventive interventions targeted at such individuals are urgently needed.

Comparison of HIV prevalences in community-based and antenatal clinic surveys in rural Mwanza, Tanzania

OBJECTIVES

First, to compare the prevalence of HIV infection among women in the general population and antenatal clinic (ANC) attenders in rural Mwanza, Tanzania, and second, to validate a method for adjusting HIV prevalence in ANC attenders to estimate the prevalence in the general female population aged 15-44 years.

METHODS

A cross-sectional population survey was conducted in 12 rural communities of Mwanza Region between 1991 and 1992. From the same communities sequential ANC attenders were recruited on two occasions between 1991 and 1993. Consenting subjects were interviewed, examined, treated and a serum sample was tested for HIV. The HIV prevalence in women in the general population was compared with unadjusted and adjusted prevalences in ANC attenders. Parity-adjusted prevalences were obtained by applying correction factors to the observed prevalences in parous and nulliparous ANC attenders.

RESULTS

A total of 5675 women aged 15-44 years from the general population and 2265 ANC attenders had complete socio-demographic and laboratory data. Unadjusted HIV prevalence was significantly lower in ANC attenders (3.6%) than women from the general population (4.7%, P = 0.025), but after adjustment there was no significant difference between the two groups (4.6 versus 4.7%, P = 0.95).

CONCLUSION

In this rural population, the HIV prevalence in ANC attenders underestimated the prevalence among women in the general population, but this difference was eliminated by applying parity-based correction factors. Information on parity should be routinely collected in ANC-based HIV sentinel surveillance.

Randomized trial of presumptive sexually transmitted disease therapy during pregnancy in Rakai, Uganda

OBJECTIVE

The purpose of this study was to assess presumptive sexually transmitted disease treatment on pregnancy outcome and HIV transmission.

STUDY DESIGN

In a randomized trial in Rakai District, Uganda, 2070 pregnant women received presumptive sexually transmitted disease treatment 1 time during pregnancy at varying gestations, and 1963 control mothers received iron/folate and referral for syphilis. Maternal-infant sexually transmitted disease/HIV and infant outcomes were assessed. Intent-to-treat analyses estimated adjusted rate ratios and 95% confidence intervals.

RESULTS

Sexually transmitted diseases were reduced: Trichomonas vaginalis (rate ratio, 0.28; 95% CI, 0.18%-0.49%), bacterial vaginosis (rate ratio, 0.78; 95% CI, 0.69-0.87), Neisseria gonorrhoeae /Chlamydia trachomatis (rate ratio, 0.43; 95% CI, 0.27-0.68), and infant ophthalmia (rate ratio, 0.37; 95% CI, 0.20-0.70). There were reduced rates of neonatal death (rate ratio, 0.83; 95% CI, 0.71-0.97), low birth weight (rate ratio, 0.68; 95% CI, 0.53-0.86), and preterm delivery (rate ratio, 0.77; 95% CI, 0.56-1.05); but there were no effects on maternal HIV acquisition or perinatal HIV transmission.

CONCLUSION

Reductions of maternal sexually transmitted disease improved pregnancy outcome but not maternal HIV acquisition or perinatal HIV transmission.

Efforts to Control Sexually Transmitted Diseases As a Means to Limit HIV Transmission: Pros and Cons

A large body of literature suggests that treatment of sexually transmitted diseases (STDs) has a measurable effect on reducing HIV infectiousness and susceptibility at both the individual and general population levels. Recent research includes biological studies on genital herpes and genital shedding of HIV-1; two large-scale, community-based clinical trials in Africa; and the use of mathematical modeling to further explore data from these landmark trials. These studies suggest that a combination of improved STD services, syndromic management, and periodic mass treatment tailored to the dynamics of the HIV/AIDS/STD epidemic in a given population can help reduce overall HIV transmission.

Risk factors for active syphilis and TPHA seroconversion in a rural African population

OBJECTIVES

Syphilis is an important cause of morbidity in sub-Saharan Africa, and a cofactor for the sexual transmission of HIV. A better understanding of the prevalence and risk factors of syphilis in African populations would help to formulate effective interventions for its prevention and treatment.

METHODS

The prevalence and incidence of syphilis were obtained from a cohort recruited in Mwanza, Tanzania. Two unmatched case-control studies nested within the cohort provide information on potential risk factors.

RESULTS

The prevalence of active syphilis (TPHA positive and RPR positive any titre) was 7.5% in men and 9.1% in women, but in youths (aged 15-19 years) the prevalence was higher in women (6.6%) than in men (2.0%). The incidence of TPHA seroconversion was highest in women aged 15-19 at 3.4% per year, and around 2% per year at all ages among men. A higher prevalence of syphilis was found in those currently divorced or widowed (men: OR=1.61, women: OR=2.78), and those previously divorced or widowed (men: OR=1.51, women: OR=1.85). Among men, prevalence was associated with lack of circumcision (OR=1.89), traditional religion (OR=1.55), and reporting five or more partners during the past year (OR=1.81) while incidence was associated with no primary education (OR=2.17), farming (OR=3.85), and a self perceived high risk of STD (OR=3.56). In women, prevalence was associated with no primary education (OR=2.13), early sexual debut (OR=1.59), and a self perceived high risk of STD (OR=3.57), while incidence was associated with living away from the community (OR=2.72).

CONCLUSION

The prevalence and incidence of syphilis remain high in this rural African population. More effort is needed to promote safer sexual behaviour, and to provide effective, accessible treatment. The high incidence of syphilis in young women calls for sexual health interventions targeted at adolescents.

Global dimensions of the AIDS epidemic: implications for prevention and care

The appropriate balance of HIV prevention and care activities depends on the specific epidemiology of HIV, including the stage of the epidemic; information about the cost-effectiveness of specific prevention interventions and treatment regimens; and the level of public resources available. In all countries, it is far less costly to prevent HIV than to treat people with AIDS. Once prevention needs are met, governments facing a severe epidemic who have additional resources should consider cost-effective treatment for people living with AIDS. The epidemiology of HIV provides two clear messages for prevention. First, it is imperative to act early in the epidemic, when HIV spreads exponentially. Viral load is highest during the first few months of infection, so that early in the epidemic a large proportion of those infected may be highly infectious. Second, it is crucial to target interventions initially to those with the highest-risk behavior. This will have the greatest impact on the number of new HIV infections prevented, as individuals with large numbers of sexual and needle-sharing partners who do not use condoms or clean injecting equipment are those most likely to become infected and then spread HIV. Changing the behavior of these individuals, even if only a relatively few members of society, is essential to curbing the epidemic.

Syndromic treatment of sexually transmitted diseases reduces the proportion of incident HIV infections attributable to these diseases in rural Tanzania

OBJECTIVES

To compare the proportion of HIV seroconversions attributable to other sexually transmitted diseases in the intervention and comparison arms of the Mwanza sexually transmitted diseases (STD) intervention trial.

DESIGN

Case-control study of 96 cases of HIV seroconversion and 974 HIV-negative controls, nested within the Mwanza trial cohort.

METHODS

Data on reported STD symptoms during 2 years of follow-up, and serological evidence of recent syphilis, were used to obtain odds ratios (ORs) for HIV seroconversion, adjusted for community, age, marital status, sex partners and travel. Population-attributable fractions (PAF) of HIV seroconversions associated with these STD exposures were calculated separately for the intervention and comparison arms, and for men and women.

RESULTS

In men in the comparison arm, adjusted ORs for ulcers (14.8), discharge (3.3), any symptom (4.1) and any STD (4.0) were highly significant. There were no significant associations between HIV incidence and STD exposures in the intervention arm. The PAF were consistently higher in the comparison arm than the intervention arm. In men, the PAF for any STD was 39.6% [95% confidence interval (CI), 12.4-58.3)] in the comparison arm but only 12.0% (CI, 0.0-35.9) in the intervention arm. The PAF for women were lower than for men.

CONCLUSIONS

These are minimal PAF estimates and they do not account for STD effects on HIV infectiousness. Nevertheless, a substantial proportion of new HIV infections in men in the comparison arm were attributable to STD. Lower PAF in the intervention arm than in the comparison arm for men provide further evidence of the role of STD cofactors in HIV transmission, supporting the hypothesis that the Mwanza intervention reduced the duration of symptomatic STD, thus reducing the HIV risk associated with such STD.

Control of sexually transmitted diseases for HIV-1 prevention: understanding the implications of the Mwanza and Rakai trials

Two randomised controlled trials of sexually transmitted disease (STD) treatment for the prevention of HIV-1 Infection, in Mwanza, Tanzania, and Rakai, Uganda, unexpectedly produced contrasting results. A decrease in population HIV-1 incidence was associated with improved STD case management in Mwanza, but was not associated with STD mass treatment in Rakai. Some reductions in curable STDs were seen in both studies. These trials tested different interventions in different HIV-1 epidemic settings and used different evaluation methods; the divergent results may be complementary rather than contradictory. Possible explanations include: differences in stage of the HIV-1 epidemic, which can influence exposure to HIV-1 and the distribution of viral load in the infected population; potential differences in the prevalence of Incurable STDs (such as genital herpes); perhaps greater Importance of symptomatic than symptomless STDs for HIV-1 transmission; and possibly greater effectiveness of continuously available services than of intermittent mass treatment to control rapid STD reinfection. Implications of the trials for policy and future research agenda are discussed.

Design and analysis issues in cluster-randomized trials of interventions against infectious diseases

This paper discusses the application of the cluster-randomized trial (CRT) design to evaluate the effectiveness of interventions against infectious diseases. In addition to the usual rationale for this design, there are a number of other advantages that are peculiar to the study of infectious diseases. In particular, CRTs are able to measure the overall effect of an intervention at the population level, capturing both the direct effect of an intervention on an individual's susceptibility to infection, and also the indirect effects due to changes in risks of transmission to other individuals, or to the mass effect or 'herd immunity' resulting from intervening in a large proportion of the population. We briefly review published CRTs of interventions against infectious diseases, most of which have been conducted in the developing countries where such diseases predominate. The focus is on trials in which communities or other large groupings are randomized, and in which impacts on infectious disease incidence or mortality are assessed. We then discuss three issues that are of special relevance to CRTs of infectious diseases. First, issues relating to the definition and size of clusters; secondly, the role of matching or stratification, and the choice of matching factors; and thirdly, the definition of direct and indirect effects of intervention, and methods of assessing these components in a CRT. We conclude by outlining some areas for future research.

Efficiency of estimating vaccine efficacy for susceptibility and infectiousness: randomization by individual versus household

In designing vaccine efficacy studies based on the secondary attack rate (SAR) or transmission probability in which both vaccine efficacy for susceptibility, VE(S), and vaccine efficacy for infectiousness, VE(I), are estimated, the allocation of vaccine and placebo within transmission units has an important influence on the efficiency of the study. We compared the following randomization schemes that result in different allocations of vaccine and placebo within two-member households: (1) randomization by individual for a mixed allocation, (2) randomization by transmission unit for concordant allocation, and (3) randomization of only one individual in each transmission unit to either vaccine or placebo. There is a complex interaction among the VE(S), VE(I), and the SAR that determines which allocation of vaccine and placebo within households provides the most information. In general, individual randomization with a mixed allocation of vaccine and placebo is better for estimating both VE(S) and VE(I) than is randomizing by household. However, for estimation of VE(I), at very low SARs and low VE(S), randomization by household is slightly more efficient than randomization by individual.

Control of sexually transmitted diseases for AIDS prevention in Uganda: a randomised community trial. Rakai Project Study Group

BACKGROUND

The study tested the hypothesis that community-level control of sexually transmitted disease (STD) would result in lower incidence of HIV-1 infection in comparison with control communities.

METHODS

This randomised, controlled, single-masked, community-based trial of intensive STD control, via home-based mass antibiotic treatment, took place in Rakai District, Uganda. Ten community clusters were randomly assigned to intervention or control groups. All consenting residents aged 15-59 years were enrolled; visited in the home every 10 months; interviewed; asked to provide biological samples for assessment of HIV-1 infection and STDs; and were provided with mass treatment (azithromycin, ciprofloxacin, metronidazole in the intervention group, vitamins/anthelmintic drug in the control). Intention-to-treat analyses used multivariate, paired, cluster-adjusted rate ratios.

FINDINGS

The baseline prevalence of HIV-1 infection was 15.9%. 6602 HIV-1-negative individuals were enrolled in the intervention group and 6124 in the control group. 75.0% of intervention-group and 72.6% of control-group participants provided at least one follow-up sample for HIV-1 testing. At enrolment, the two treatment groups were similar in STD prevalence rates. At 20-month follow-up, the prevalences of syphilis (352/6238 [5.6%]) vs 359/5284 [6.8%]; rate ratio 0.80 [95% CI 0.71-0.89]) and trichomoniasis (182/1968 [9.3%] vs 261/1815 [14.4%]; rate ratio 0.59 [0.38-0.91]) were significantly lower in the intervention group than in the control group. The incidence of HIV-1 infection was 1.5 per 100 person-years in both groups (rate ratio 0.97 [0.81-1.16]). In pregnant women, the follow-up prevalences of trichomoniasis, bacterial vaginosis, gonorrhoea, and chlamydia infection were significantly lower in the intervention group than in the control group. No effect of the intervention on incidence of HIV-1 infection was observed in pregnant women or in stratified analyses.

INTERPRETATION

We observed no effect of the STD intervention on the incidence of HIV-1 infection. In the Rakai population, a substantial proportion of HIV-1 acquisition appears to occur independently of treatable STD cofactors.

A randomized, community trial of intensive sexually transmitted disease control for AIDS prevention, Rakai, Uganda

OBJECTIVE

To describe the design and first-round survey results of a trial of intensive sexually transmitted disease (STD) control to reduce HIV-1 incidence.

STUDY DESIGN

Randomized, controlled, community-based trial in Rakai District, Uganda.

METHODS

In this ongoing study, 56 communities were grouped into 10 clusters designed to encompass social/sexual networks; clusters within blocks were randomly assigned to the intervention or control arm. Every 10 months, all consenting resident adults aged 15-59 years are visited in the home for interview and sample collection (serological sample, urine, and, in the case of women, self-administered vaginal swabs). Sera are tested for HIV-1, syphilis, gonorrhea, chlamydia, trichomonas and bacterial vaginosis. Following interview, all consenting adults are offered directly observed, single oral dose treatment (STD treatment in the intervention arm, anthelminthic and iron-folate in the control arm). Treatment is administered irrespective of symptoms or laboratory testing (mass treatment strategy). Both arms receive identical health education, condom and serological counseling services.

RESULTS

In the first home visit round, the study enrolled 5834 intervention and 5784 control arm subjects. Compliance with interview, sample collection and treatment was high in both arms (over 90%). Study arm populations were comparable with respect to sociodemographic and behavioral characteristics, and baseline HIV and STD rates. The latter were high: 16.9% of all subjects were HIV-positive, 10.0% had syphilis, and 23.8% of women had trichomonas and 50.9% had bacterial vaginosis.

CONCLUSIONS

Testing the effects of STD control on AIDS prevention is feasible in this Ugandan setting.

Cost-effectiveness of improved treatment services for sexually transmitted diseases in preventing HIV-1 infection in Mwanza Region, Tanzania

BACKGROUND

A community-randomised trial was undertaken to assess the impact, cost, and cost-effectiveness of averting HIV-1 infection through improved management of sexually transmitted diseases (STDs) by primary-health-care workers in Mwanza Region, Tanzania.

METHODS

The impact of improved treatment services for STDs on HIV-1 incidence was assessed by comparison of six intervention communities with six matched communities. We followed up a random cohort of 12,537 adults aged 15-54 years for 2 years to record incidence of HIV-1 infection. The total and incremental costs of the intervention were estimated (ingredients approach) and used to calculate the total cost per case treated, the incremental cost per HIV-1 infection averted, and the incremental cost per disability-adjusted life-year (DALY) saved.

FINDINGS

During 2 years of follow-up, 11,632 cases of STDs were treated in the intervention health units. The baseline prevalence of HIV-1 infection was 4%. The incidence of HIV-1 infection during the 2 years was 1.16% in the intervention communities and 1.86% in the comparison communities. An estimated 252 HIV-1 infections were averted each year. The total annual cost of the intervention was US$59,060 (1993 prices), equivalent to $0.39 per head of population served. The cost for STD case treated was $10.15, of which the drug cost was $2.11. The incremental annual cost of the intervention was $54,839, equivalent to $217.62 per HIV-1 infection averted and $10.33 per DALY saved (based on Tanzanian life expectancy) or $9.45 per DALY saved (based on the assumptions of the World Development Report). In a sensitivity analysis of factors influencing cost-effectiveness, cost per DALY saved ranged from $2.51 to $47.86.

INTERPRETATION

Improved management of STDs in rural health units reduced the incidence of HIV-1 infection in the general population by about 40%. The estimated cost-effectiveness of this intervention ($10 per DALY) compares favourably with that of, for example, childhood immunisation programmes ($12-17 per DALY). Cost-effectiveness should be further improved when the intervention is applied on a larger scale. Resources should be made available for this highly cost-effective HIV control strategy.

Decline in maternal mortality in Matlab, Bangladesh: a cautionary tale

BACKGROUND

A study in Matlab, Bangladesh, has provided evidence favouring a community-based maternity-care delivery system. 3 years of this programme coincided with a significant reduction in direct obstetric mortality compared with the 3 years before the programme. We have examined whether the effects of the programme are sustained over time.

METHODS

Using data from the continuing demographic survelliance system and from special investigations into the rates and causes of maternal mortality during 1976-93, we compared the trends in direct obstetric maternal mortality ratios in the Maternal and Child Health and Family Planning (MCH-FP) area (which has received extensive services in health and family planning since 1977) with those in the comparison area (with no such intensive health inputs). We divided the areas and time periods into discrete groups that best represented the effects of the introduction of the maternity-care programme.

FINDINGS

Direct obstetric mortality declined by 3% per year (rate ratio 0.97 per year [95% CI 0.95-0.99]); there was no difference between the MCH-FP and comparison areas (1.00 [0.96-1.05]). Direct obstetric mortality halved between 1976-86 and 1987-89 in the northern MCH-FP area, where the maternity-care programme was initiated in 1987 (0.50 [0.22-0.99]), but showed no change in the southern MCH-FP area, which had no such intervention at that time (1.07 [0.64-1.72]). After 1990, when the programme was expanded throughout the MCH-FP area, the southern part showed a downward (non-significant) trend in direct obstetric mortality (0.68 [0.35-1.32]). However, direct obstetric mortality also declined between 1987 and 1989 in the southern comparison area (0.48 [0.26-0.83]) in the absence of an intense maternity-care programme, and remained stable thereafter. In the northern comparison area, there was no such decline in direct obstetric mortality (0.78 [0.40-1.40]).

INTERPRETATION

Although the introduction of the maternity-care programme coincided with declining trends in direct obstetric mortality in the areas covered by the programme, a decline also occurred in one of the areas not receiving any such interventions. Caution is required in the interpretation of short-term trends in one indicator in studies designed without random allocation of interventions into treatment and control groups.

Randomised trials of STD treatment for HIV prevention: report of an international workshop. HIV/STD Trials Workshop Group

Three community trials of the impact of STD treatment interventions on HIV incidence in rural populations have been completed or are in progress in Uganda and Tanzania. Investigators from these trials met for a joint technical workshop in Baltimore in May 1996. This report summarises the consensus of the workshop, with the aim of providing useful input to research on HIV intervention strategies. Issues discussed include: (i) the role of community randomised trials; (ii) strategies for STD management; (iii) epidemiological and statistical issues in the design and analysis of community randomised trials; (iv) diagnostic methods for STDs in population surveys; (v) treatment regimens for STDs in rural Africa; and (vi) ethical issues in community trials.

The advantages of community-randomized trials for evaluating lifestyle modification

Observational studies may provide suggestive evidence for the results of behavior change and lifestyle modification, but they do not replace randomized trials for comparing interventions. To obtain a valid comparison of competing intervention strategies, randomized trials of adequate size are the recommended approach. Randomization avoids bias, achieves balance (on average) of both known and unknown predictive factors between intervention and comparison groups, and provides the basis of statistical tests. The value of randomization is as relevant when investigating community interventions as it is for studies that are directed at individuals. Randomization by group is less efficient statistically than randomization by individual, but there are reasons why randomization by group (such as community) may be chosen, including feasibility of delivery of the intervention, political and administrative considerations, avoiding contamination between individuals allocated to competing interventions, and the very nature of the intervention. One example is the Community Intervention Trial for Smoking Cessation (COMMIT), which involved 11 matched pairs of communities and randomized within these pairs to active community-level intervention versus comparison. For analysis of results, community-level permutation tests (and corresponding test-based confidence intervals) can be designed based on the randomization distribution. The advantages of this approach are that it is robust, and the unit of randomization is the unit of analysis, yet it can incorporate individual-level covariates. Such covariates can play a role in imputation for missing values, adjustment for imbalances, and separate analyses in demographic subsets (with appropriate tests for interaction). A community-randomized trial can investigate a multichannel community-based approach to lifestyle modification, thus providing generalizability coupled with a rigorous evaluation of the intervention.

Improved treatment services significantly reduce the prevalence of sexually transmitted diseases in rural Tanzania: results of a randomized controlled trial

OBJECTIVE

To evaluate the impact of improved case management for sexually transmitted diseases (STD) at the primary health care level on the incidence and prevalence of STD.

DESIGN

Community-randomized controlled trial.

SETTING

Mwanza region, Tanzania.

SUBJECTS

A random cohort of about 1000 adults aged 15-54 years from each of 12 communities, in six matched pairs. One member of each pair was assigned at random to receive the intervention, and the others served as a comparison community. This cohort was surveyed at baseline and at follow-up 2 years later. About 100 antenatal clinic attenders were also studied in each community on two occasions: the first shortly after the implementation of the intervention, and the second approximately 1 year later.

INTERVENTION

Improved services were established for the management of STD, using the syndromic approach, in rural health units.

RESULTS

A total of 12,534 individuals were enrolled in the cohort study, of whom 8844 (71%) were seen again 2 years later. The prevalence of serological syphilis (rapid plasma reagin titre > or = 1:8, Treponema pallidum haemagglutinin assay positive) was 6.2% in both intervention and comparison communities at baseline. At follow-up it was 5.0% in the intervention community and 7.0% in the comparison community [adjusted relative risk (RR), 0.71; 95% confidence interval (CI), 0.54-0.93; P < 0.02]. The prevalence of urethritis in males did not differ significantly between intervention and comparison groups at follow-up, but the prevalence of symptomatic urethritis was reduced by about 50% (adjusted RR, 0.51; 95% CI, 0.24-1.10; P = 0.08). There was no significant difference between the groups in the incidence of self-reported STD symptoms over the last year of the follow-up period, or in the prevalence of any STD in antenatal clinic attenders.

CONCLUSION

The reduction in HIV incidence previously reported in this intervention study can be attributed to a reduction in the duration, and hence the prevalence of symptomatic STD.

HIV-associated adult mortality in a rural Tanzanian population

OBJECTIVE

To measure HIV-associated adult mortality in a rural population in Tanzania. To record the signs and symptoms associated with deaths of HIV-positive adults.

DESIGN

Prospective cohort study conducted in the context of a randomized controlled trial to evaluate the impact of a sexually transmitted disease treatment programme.

METHODS

A cohort consisting of a random sample of 12501 adults aged 15-54 years was recruited from 12 rural communities in Mwanza region, Tanzania in 1991/1992. Baseline HIV prevalence was 4.0%. The cohort was followed up after 2 years to record mortality according to baseline HIV status. A verbal autopsy questionnaire was administered for each of the deaths reported.

RESULTS

A total of 196 deaths were recorded, of which 73 (37%) occurred in HIV-positive individuals. Mortality rates per 1000 person-years were 6.0 in HIV-negatives and 93.5 in HIV-positives. The age-adjusted mortality rate ratio was 15.68 (95% confidence interval, 11.18-21.03). The proportion of adult deaths attributed to HIV infection was 35% overall and 53% in those aged 20-29 years. Verbal autopsies showed that HIV-positive deaths were significantly associated with fever, rash, weight loss, anaemia, cough, chest pain, abdominal pain and headache, but the specificity of individual symptoms was low. The World Health Organization clinical case definition of AIDS was satisfied for only 13 deaths, of which seven were HIV-positive at baseline. Only seven respondents reported that the death was associated with HIV or AIDS.

CONCLUSIONS

This study confirms the strong association of HIV infection and mortality in rural Africa, with an annual death rate in adult seropositives of over 9%. In this rural population with a relatively low HIV prevalence of 4%, HIV has increased overall adult mortality by more than 50%. Signs and symptoms associated with HIV deaths were non-specific, and the population seemed largely unaware of the contribution of HIV to mortality, an important obstacle to prevention efforts.

Patterns of sexual behaviour in a rural population in north-western Tanzania

The HIV epidemic in sub-Saharan Africa has been characterised by the predominance of heterosexual transmission. Patterns of sexual behaviour have been implicated in the spread of the epidemic, but few quantitative data are available on sexual behaviour in rural populations in Africa. This paper reports data from a survey of 1117 adults aged 15-54 years selected randomly from twelve rural communities in Mwanza Region, Tanzania. Sexual debut occurred early, 50% of women and 46% of men reporting first sex before age 16. On average, women married 1.8 years and men 6.1 years after their sexual debut. In women, age at sexual debut appears to have increased over time, in parallel with an increase in age at first marriage. Men were generally married later, to women around five to ten years younger than themselves. Marital dissolution and remarriage were common in both sexes. Reported numbers of sexual partners were compared with those recorded in a population survey in Britain. More men reported 10 or more lifetime partners, or three or more partners in the past year, in rural Mwanza (48% and 29%) than in Britain (24% and 6%). Women reported fewer partners, and results were broadly similar to British data. Casual sex during the past year was reported by 53% of the men and 15% of the women, but only 2% of men reported sexual contact with bar girls or commercial sex workers. Only 20% of men and 3% of women had ever used a condom. Interventions are needed to reduce the high levels of sexual partner change and casual sex, and low levels of condom use, recorded in this rural population. Targeting of interventions to traditional "core groups" may be of limited value in rural areas, and additional strategies are needed, focusing particularly on teenagers who are at high risk of HIV and other sexually transmitted diseases.

Male circumcision and susceptibility to HIV infection among men in Tanzania

BACKGROUND

Evidence from ecological studies and from studies of and sexually transmitted disease (STD) patients in sub-Saharan Africa suggests that there is a protective effect of male circumcision against HIV infection. There are, however, few population-based studies that have controlled adequately for potential confounding factors.

METHODS

Data from the five population-based studies in north-western Tanzania were used to investigate the association between male circumcision and the risk of HIV infection and STD. The effects of circumcision on HIV prevalence, syphilis (positive Treponema pallidum haemagglutination; TPHA) and self-reported STD were analysed, controlling for a range of demographic and sociocultural variables, and indicators of sexual behaviour.

RESULTS

In north-western Tanzania, circumcision was previously restricted to Muslims and specific ethnic groups, but is now more widespread, particularly in urban ares and among more educated men. Assessment of the reliability and validity of self-reported circumcision status showed that these data could be considered fairly accurate, although there was some tendency for circumcision to be over-reported. On univariate analysis, circumcision status was unrelated to HIV prevalence in most studies. After controlling for confounding variables, however, there was a modest but significant reduction of the HIV prevalence among circumcised men [odds ratio (OR), 0.62; 95% confidence interval (CI), 0.48-.81]. This effect appeared stronger in urban areas (OR, 0.46; 95% CI, 0.32-0.68) and roadside villages (OR, 0.65; 95% CI, 0.42-1.01) than in rural areas and islands (OR, 1.00 and 1.01 respectively). There was no association between circumcision status and syphilis serology (TPHA), but there was a positive association between circumcision and self-reported STD, although this was not significant after adjustment for confounding variables.

CONCLUSION

Male circumcision has a protective effect against HIV infection in this population, which may be stronger in urban areas and roadside settlements than in the rural areas. Ethnic group and religious denomination are no longer the sole determinants of male circumcision.

Sexual behaviour patterns and other risk factors for HIV infection in rural Tanzania: a case-control study

OBJECTIVE

To examine the association between HIV infection and patterns of sexual behaviour and other risk factors in a rural Tanzanian population in a case-control study, nested within a randomized trial of improved sexually transmitted disease treatment.

METHODS

All HIV-positive patients from the baseline survey of the randomized trial were eligible as cases. Cases (n = 338) and controls (a random sample of one in eight HIV-negative persons; n = 1078) were interviewed about risk factors for HIV infection using a structured questionnaire.

RESULTS

A significantly higher HIV prevalence was found among men and women not currently employed in farming [men: odds ratio (OR), 2.08; women: OR, 3.65], women who had travelled (OR, 3.27), educated women (OR, 4.51), and widowed/ divorced people compared with those currently married (men: OR, 3.10; women: OR, 3.54). Two spouse-related factors were significantly associated with HIV, even after adjustment for the sexual behaviour of the index case: HIV was more prevalent in men with younger spouses (P = 0.020 for trend) and in women married to men currently employed in manual work, office work or business (OR, 2.20). In women only, blood transfusions were associated with a higher HIV prevalence (OR, 2.40), but only a small population attributable fraction (4%). There was an increased HIV prevalence associated with increasing numbers of injections. Reported number of lifetime sexual partners was significantly associated with HIV infection (women: OR, 7.33 if > or = 10 lifetime partners compared with < or = 1; men: OR, 4.35 for > or = 50 compared with < or = 1). After adjustment for confounders, male circumcision was associated with a lower HIV prevalence (OR, 0.65; P = 0.11).

CONCLUSIONS

In these rural communities, many HIV infections occur through sexual transmission. Some people are at high risk of HIV infection through large numbers of sex partners, whereas some are at risk through their spouse or regular partner. The role of circumcision in HIV transmission is unclear. Commercial sex seems to play a negligible role in HIV transmission in these communities. Our results confirm marked heterogeneity in HIV risk, indicating the scope for risk reduction strategies.

Male circumcision and susceptibility to HIV infection among men in Tanzania

BACKGROUND

Evidence from ecological studies and from studies of and sexually transmitted disease (STD) patients in sub-Saharan Africa suggests that there is a protective effect of male circumcision against HIV infection. There are, however, few population-based studies that have controlled adequately for potential confounding factors.

METHODS

Data from five population-based studies in north-western Tanzania were used to investigate the association between male circumcision and the risk of HIV infection and STD. The effects of circumcision on HIV prevalence, syphilis (positive Treponema pallidum haemagglutination; TPHA) and self-reported STD were analysed, controlling for a range of demographic and sociocultural variables, and indicators of sexual behaviour.

RESULTS

In north-western Tanzania, circumcision was previously restricted to Muslims and specific ethnic groups, but is now more widespread, particularly in urban areas and among more educated men. Assessment of the reliability and validity of self-reported circumcision status showed that these data could be considered fairly accurate, although there was some tendency for circumcision to be over-reported. On univariate analysis, circumcision status was unrelated to HIV prevalence in most studies. After controlling for confounding variables, however, there was a modest but significant reduction of the HIV prevalence among circumcised men [odds ratio (OR), 0.62; 95% confidence interval (CI), 0.48-0.81]. This effect appeared stronger in urban areas (OR, 0.46; 95% CI, 0.32-0.68) and roadside villages (OR, 0.65; 95% CI, 0.42-1.01) than in rural areas and islands (OR, 1.00 and 1.01 respectively). There was no association between circumcision status and syphilis serology (TPHA), but there was a positive association between circumcision and self-reported STD, although this was not significant after adjustment for confounding variables.

CONCLUSION

Male circumcision has a protective effect against HIV infection in this population, which may be stronger in urban areas and roadside settlements than in the rural areas. Ethnic group and religious denomination are no longer the sole determinants of male circumcision.