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Department of Biostatistics HIV Working Group 2009 - 2010 |
ABSTRACT: With an antenatal HIV prevalence of 37% in 2007, the South African province of KwaZulu-Natal suffers from one of the worst HIV epidemics worldwide. This talk introduces research conducted in a demographic surveillance site in rural KwaZulu-Natal, the Africa Centre for Health and Population Studies, on measurement, levels, and determinants of HIV incidence, clustering of HIV prevalence, and recent trends in adult mortality.
ABSTRACT: The HIV-1/AIDS pandemic is with over 33 million infected people worldwide and 2 million AIDS deaths each year the most devastating infectious disease in recent history. While highly active antiretroviral therapy (HAART) has been successfully developed, limited access and high costs likely preclude it from slowing the epidemic. An effective HIV-1 vaccine is therefore urgently needed. The recent failure of the Merck vaccine trial and the unexpected modest success of a vaccine consisting of a combination of two vaccine candidates (ALVAC and AIDSVAX) drastically demonstrate that much more understanding is required to develop an effective vaccine. The identification of definitive determinants and correlates of HIV control in vivo has been shown to be one of the most challenging quests in HIV research and has thus far brought only mixed results. The complex cause-and-effect relationship of the co-evolving processes of immune responses, immune dysfunction and viral evolution makes the identification and interpretation of potential correlations difficult. In this presentation we will re-assess findings in HIV-1 immunology and will discuss the cause or consequence relationships. We will also present new preliminary data on HIV-1-specific CD4+ T cells and will discuss the potential role of these cells in the control of viral replication.
ABSTRACT: The roll-out of antiretroviral treatment (ART) in sub-Saharan settings has generated significant improvement in health outcomes, and has showed promise in reducing the onward transmission of HIV infection. However, the full potential of HAART has not been reached, and its population-level impact remains limited in sub-Saharan settings because (i) the uptake of HIV testing and counseling (HTC) is low, and (ii) affected individuals present for testing at already advanced stages of the disease. Increasing the case finding capacity of sub-Saharan health systems is thus a crucial HIV control priority. Current approaches to increasing HIV case finding all rely on screening mechanisms (e.g., routine testing in clinical settings, door-to-door HIV testing). In this presentation, I use unique data on the sexual networks connecting members of a small island population of Northern Malawi to suggest that contact tracing may be an important, but so far neglected, tool for HIV control in generalized epidemics. I describe, in details, the sociocentric cohort data on sexual networks collected between 2005 and 2008 on Likoma Island. I then describe partner tracing outcomes obtained during the study, and provide initial estimates of the prevalence of HIV infection among both marital and concurrent casual partners of HIV index cases (a previously unknown parameter). I end by discussing the possible benefits and incremental costs attached to contact tracing, as well as its operational feasibility.
ABSTRACT: Using observational data, we estimate the effect of treatment regimes that initiate treatment depending on time since infection. The main complication with observational data is that treatment was not randomly assigned. E.g., if sicker patients were treated earlier, this may lead to underestimation of the effect of treatment, or even reverse a possible effect. Our identifying assumption is that there are no unmeasured confounders. We develop a new class of Structural Nested Models (SNMs) to estimate the impact of time of initiation of treatment after infection on an outcome measured one year after initiation, compared to the effect of not initiating treatment.We illustrate our methods using the AIEDRP Core01 database on HIV. The current standard of care in HIV positive patients is Highly Active Anti-Retroviral Treatment (HAART). However, it is unknown yet what is the best time to start HAART, and guidelines are changing. Perhaps postponing HAART is beneficial, because it postpones the time patients experience side effects or develop drug resistance, and hence might improve the patients' long term prognosis. However, it is unknown how long initiation of HAART can safely be postponed without irreversible immune system damage. We investigate the effect of initiating HAART at different times following HIV infection on immune reconstitution measured one year after initiation.
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