Programme Supplement [International Conference on AIDS (16th: 2006: Toronto, Canada)]

Late Breaker Abstracts

Background: Pre-exposure prophylaxis (PrEP) is an unproven
HIV prevention strategy being evaluated in clinical trials. Multiple
media reports and a 2004 convenience survey suggested
substantial PrEP use outside clinical trials; such use has potential
for individual and community harm. We assessed PrEP knowledge
and use among three populations of HIV-negative/unknown gay/
bisexual men. /
Methods: We collected in-depth information from 579 gay/
bisexual men self-reporting negative or unknown HIV serostatus
from 1) SF: 403 men residing in the San Francisco Bay Area using
time location probability sampling from February to May 2006, and
2) CP: 176 men attending a circuit party in Palm Springs in April
2006. Additionally, 217 men attending the San Francisco STD clinic
(STD) in April and May 2006 completed a brief questionnaire about
PrEP knowledge and use. We used multivariate logistic regression
to assess correlates of PrEP awareness among SF and CP.
Results: In SF and CP combined, 60% were white and 41%
reported unprotected anal sex in the past six months. Only 19%
were aware of PrEP, and no respondents reported PrEP use (95%
CI 0-0.7%). Respondents most commonly heard about PrEP
through newspapers/magazines (47%) and friends/acquaintances
(22%). Only one demographic or risk variable was associated
with PrEP awareness: unprotected anal sex in the past 6 months
(OR=2.0, CI 1.3-3.0). In STD, 15% reported PrEP awareness, and
1/207 (0.48%) reported prior PrEP use. This individual, however,
reported he had not heard of PrEP and reported his provider gave
him 30 days of medication, suggesting this might have been postexposure prophylaxis.
Conclusions: PrEP awareness was low in three distinct populations
of HIV negative/unknown gay/bisexual men, and only one man
reported possible PrEP use. PrEP use appears to be an uncommon
practice, contrary to prior reports, but should continue to be
monitored while awaiting clinical trial results.
THLB0102
Cost-effectiveness analysis of HIV chemoprophylaxis
R. Grant1, J. Lama2, P. Goicochea2, V. Levy1, T. Porco3. 'Gladstone
Institute of Virology and Immunology and University of California,
San Francisco, San Francisco, United States, 2Asociacion Civil
Impacta Salud y Educacion, Lima, Peru, 3Department of Health
Services, California State, Berkeley, United States
Background: HIV continues to spread despite access to counseling
and condoms. Chemoprophylaxis (pre-exposure prophylaxis
or PrEP) with systemic microbicides containing generally welltolerated antiretroviral agents is being evaluated in clinical trials in
the US, Africa, Asia, and Latin America. Ethical guidelines require
the research be performed in populations where the intervention
would be feasible if the trials demonstrate efficacy with acceptable
safety.
Methods: Population effects and cost effectiveness were
simulated using a mathematical model that considers heterosexual
and homosexual transmission, higher infectiousness in early
and late infection, age and sex effects on susceptibility, risk
behavior variation, condom replacement, known age-sex partner
preferences, and primary and secondary drug resistance.
Results: Benefits and risks accrue primarily among PrEP users.
Reductions in secondary transmission from PrEP users were also
important, especially if PrEP lowers viral load during primary
infection and prevents some infections altogether. Increases in
risk behavior (either increases in partner numbers or condom
replacement) offsets PrEP benefits if efficacy is modest (in
the 50% to 80% range) but is less deleterious if PrEP is highly
effective. The effects of drug resistance are longer term, and
depend on the epidemiological characteristics of drug resistant
variants, including transmission fitness and duration as the
major transmissible variant. Cost effectiveness depends strongly
on laboratory costs for screening and monitoring. Inclusion of
hepatitis B infected persons improves cost effectiveness in most
scenarios.
Conclusions: Prevention of HIV infection is more cost effective
than treatment. If PrEP is found to be highly efficacious, PrEP
implementation is expected to be affordable where a commitment

to antiretroviral treatment exists. The level of laboratory monitoring
required for PrEP is being studied, and is a predominant factor in
cost effectiveness analysis. The utility of PrEP depends on a wide
range of social, economic, and biological factors, which should be
specifically evaluated where HIV transmission is occurring.
THLB0103
Findings from a double-blind, randomized, placebocontrolled trial of tenofovir disoproxil fumarate (TDF) for
prevention of HIV infection in women
L. Peterson1, D. Taylor', E.E.K. Clarke2, A.S. Doha, P. Phillips1, G.
Belai', K. Nanda1, R. Ridzon4, H.S. Jaffe5, W. Cates1. 'Family Health
International, Durham, North Carolina, United States, 2Ministry of
Health, Accra, Ghana, 3University of Yaounde, Yaounde, Cameroon,
4Bill & Melinda Gates Foundation, Seattle, Washington, United
States, 5Gilead Sciences, Inc., Foster City, California, United
States
Background: Animal studies have suggested that TDF may be
effective for prophylaxis against l-IV infection. We investigated
the safety and preliminary prophylactic effectiveness of a daily
dose of 300 mg TDF versus placebo in HIV-uninfected women.
Methods: Between June 2004 and March 2005, we enrolled 936
HIV-negative women into a double-blind, randomized trial (1:1
TDF:placebo) in Ghana, Cameroon, and Nigeria. Participants made
up to 12 monthly visits for study drug re-supply, HIV testing
and adverse event (AE) reporting. Laboratory testing (serum
creatinine, phosphorus, ALT, and AST) was done quarterly, and
ALT/AST levels were monitored in a subset of participants after
study drug was withdrawn. Analysis of laboratory abnormalities
was restricted to data from Ghana and Cameroon.
Results: The most common AEs were malaria, candidiasis,
headache, abdominal pain, and dizziness, with no significant
differences between treatment groups. Furthermore, no
significant differences emerged between groups for Grade 3 or
higher laboratory abnormalities. Specifically, none of the 363
participants in the TDF group had ALT or AST elevations greater
than 170 U/L prior to product withdrawal, and 2/368 and 3/368
of the participants in the placebo group had elevated (>170 U/
L) ALT and AST levels, respectively. Two participants in the TDF
group and one in the placebo group had decreases in phosphorus
to less than 1.5 mg/dL. One participant in the placebo group had
a creatinine elevation greater than 3.0 mg/dL. Two HIV infections
were diagnosed in participants randomized to TDF (rate = 0.86 per
100 person-years) and six in participants receiving placebo (rate
= 2.48 per 100 person-years), yielding a rate ratio of 0.35 (95%
confidence interval = 0.03-1.93).
Conclusions: TDF did not increase the rate of adverse events or
Grade 3-4 laboratory abnormalities in participants during or after
use. The number of HIV infections was insufficient to conclude that
TDF protected against HIV infection.
THLB0104
Harm reduction success as needle exchange programme
distributes safer crack smoking resources
L.E. Leonard, E. Meadows, L. Pelude, J. Seto, N. Birkett, E.
Medd. University of Ottawa, Epidemiology and Community
Medicine, Ottawa, Canada
Background: Despite emerging evidence documenting the
potential for HIV transmission through the multi-person use of
implements to smoke crack, the HIV-related prevention needs
of people who smoke crack have largely been ignored in the
development and implementation of harm reduction programmes
for people who inject drugs (IDUs). In the context of some of the
highest Canadian prevalence rates of HIV (20.6%) and HCV (75.8%)
among IDUs, in April 2005 Ottawa's Public Health Department
implemented an initiative to reduce the harms associated with
smoking crack. Through the Safer Crack Use Initiative, glass
stems, rubber mouthpieces, screens, and other harm reduction
resources are distributed by the city's needle exchange programme

I (NEP). The objective of this study was to evaluate the impact of

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XVI INTERNATIONAL AIDS CONFERENCE * 13-18 AUGUST 2006 * TORONTO CANADA * PROGRAMME SUPPLEMENT