Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Adolescents are regarded as a high risk group in South Africa with the highest
human immunodeficiency virus (HIV) incidence occurring in this group. Prevention
among adolescents is therefore a key in decreasing the HIV burden.
This thesis aims to assist in the design of trials by simulating the potential outcomes
of a combination prevention trial in adolescents. We develop a stochastic
individual-based model stratified by sex and age. We then use this model to
determine the impact of various prevention packages on HIV incidence among
adolescents participating in a hypothetical trial over a three year period. The
trial that is simulated involves an intervention arm, in which adolescents are
offered a choice of a prevention methods (including medical male circumcision
(MMC), oral pre-exposure prophylaxis (PrEP) and antiretroviral-based vaginal
microbicides (ARV-VM)), and a control arm. We predict that the impact
of a full prevention package on HIV incidence would be a 46% per personyear(
PPY) (95% CI 45–47%) risk reduction. The combination of MMC and
PrEP 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 of
PrEP, a microbicide gel or a microbicide in the form of a vaginal ring would be
less effective, with a 57% PPY (95% CI 56–58%) relative risk of HIV acquisition.
This is not substantially different from the relative risk estimated when
the 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 requirement
of approximately 1013 in each arm of a trial would achieve 80% power to detect
a statistically significant reduction in HIV risk. We find that the relative risk
is sensitive to the assumed degree of correlation between condom use and the
acceptability of the prevention method. We also find that the most efficient
trial design may be to offer both MMC and PrEP to males but to offer only
a microbicide ring to females. Further work is required to better understand
the processes by which adolescent prevention method choices are made. / AFRIKAANSE OPSOMMING: Adolessente word beskou as ‘n hoe risiko groep in Suid Afrika, met die hoogste
menslike immuniteitsgebrekvirus (MIV) insidensie in hierdie groep. Voorkoming
van MIV onder adolessente is daarom noodsaaklik om die MIV las te
verminder. Die doel van hierdie tesis is om te help met die ontwerp van studies
deur die moontlike uitkomste van ‘n kombinasie-voorkoming studie in adolessente
te simuleer. Ons het ‘n stogastiese individu-gebaseerde model, gestratifiseer
met betrekking tot seks en ouderdom, ontwikkel. Ons het toe die model
gebruik om die impak van ‘n verskeinheid van voorkomingspakette op MIV insidensie
onder adolessente wat deelneem aan ‘n hipotetiese proef oor ‘n drie jaar
periode, te bepaal. Die proef wat gesimuleer word behels a intervensie groep,
waarin die jong volwassenes ‘n keuse van voorbehoedings metodes (insluitende
mediese manlike besnydenis (MMB), pre-blootstelling profilakse (PrBP) en
anti-retrovirale vaginale mikrobisiedes (ARV-VM)) aangebied word, en ‘n kontrole
groep. Ons voorspel dat die impak van ‘n volle voorkomingspaket op MIV
insidensie ‘n 46% per persoon-jaar (PPJ) (95% VI 47–47%) risiko vermindering
sal wees. Die kombinasie van MMB en PrBP het ‘n substansiele impak
op MIV insidensie onder mans, met ‘n relatiewe risiko van MIV infeksie van
51% PPJ (95% VI 49–53%). Om die keuse van PrBP, ‘n mikrobisiede gel of
‘n mikrobisiede in die vorm van ‘n vaginale ring aan vrouens te bied, is minder
effektief, met ‘n relatiewe risiko van MIV infeksie van 57% PPJ (95% VI 56%–58%). Hierdie verskil nie substansieel van die beraamde relatiewe risiko
in die geval waar slegs die vaginale ring gebied word nie, aangesien daar aanvaar
word dat die ring die mees aanvaarde van die drie voorkomingsmetodes is.
Ons het bepaal dat ‘n steekproef van ongeveer 1013 individue in elke arm van
die proef nodig is om ‘n 80% kans te he om ‘n statisties betekenisvolle afname
in MIV-risiko te bespeur. Ons vind dat die relatiewe risiko sensitief is tot die
aanvaarde graad van die korrelasies tussen kondoom-gebruik en die aanvaarding
van die voorkomings metodes. Ons het ook gevind dat dit mag wees dat
die mees doeltreffende proef ontwerp is om beide MMB en PrBP vir mans en
slegs ‘n mikrobisiede ring vir vrouens te bied. Verdere werk word benodig om
die prosesse waarby jong volwassenes keuses maak oor voorkomingsmetodes te
verstaan.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/85666 |
| Date | 12 1900 |
| Creators | Bruce, Faikah |
| Contributors | Johnson, L. F., Welte, A., Stellenbosch University. Faculty of Science. Dept. of Mathematical Sciences. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 100 p. : ill. |
| Rights | Stellenbosch University |
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