Understanding the impact of an HIV intervention package for adolescents

[摘要] ENGLISH ABSTRACT: Adolescents are regarded as a high risk group in South Africa with the highesthuman immunodeficiency virus (HIV) incidence occurring in this group. Preventionamong adolescents is therefore a key in decreasing the HIV burden.This thesis aims to assist in the design of trials by simulating the potential outcomesof a combination prevention trial in adolescents. We develop a stochasticindividual-based model stratified by sex and age. We then use this model todetermine the impact of various prevention packages on HIV incidence amongadolescents participating in a hypothetical trial over a three year period. Thetrial that is simulated involves an intervention arm, in which adolescents areoffered a choice of a prevention methods (including medical male circumcision(MMC), oral pre-exposure prophylaxis (PrEP) and antiretroviral-based vaginalmicrobicides (ARV-VM)), and a control arm. We predict that the impactof a full prevention package on HIV incidence would be a 46% per personyear(PPY) (95% CI 45–47%) risk reduction. The combination of MMC andPrEP has a substantial impact on HIV incidence in males, with a 51% PPY(95% CI 49–53%) relative risk of HIV infection. Offering women the choice ofPrEP, a microbicide gel or a microbicide in the form of a vaginal ring would beless effective, with a 57% PPY (95% CI 56–58%) relative risk of HIV acquisition.This is not substantially different from the relative risk estimated whenthe vaginal ring alone is offered, as the ring is assumed to be the most accept able of the three prevention methods. We determine a sample size requirementof approximately 1013 in each arm of a trial would achieve 80% power to detecta statistically significant reduction in HIV risk. We find that the relative riskis sensitive to the assumed degree of correlation between condom use and theacceptability of the prevention method. We also find that the most efficienttrial design may be to offer both MMC and PrEP to males but to offer onlya microbicide ring to females. Further work is required to better understandthe processes by which adolescent prevention method choices are made.

[发布机构] Stellenbosch University