Meta-analysis
Shows Very Low Risk of Heterosexual Transmission if HIV Positive Partner is on
Antiretroviral Therapy with Undetectable Viral Load By
Liz Highleyman Over
the past few years, there has been considerable debate about the risk of HIV transmission
if the HIV positive partner is receiving effective antiretroviral
treatment and has an undetectable HIV viral load. In
January 2008, the
Swiss Federal Commission for HIV/AIDS issued a statement indicating that HIV
positive individuals on antiretroviral therapy (ART) who are fully adherent, maintain
an undetectable viral HIV RNA level for at least 6 months, and have no concurrent
sexually transmitted infections for all intents and purposes cannot transmit HIV
via heterosexual vaginal intercourse. Some experts have suggested that treating
everyone with HIV, regardless of CD4 cell count, might
be an effective prevention strategy. In
an effort to synthesize evidence in this area, Suzanna Attia from the University
of Bern in Switzerland and colleagues conducted a systematic review and meta-analysis
of studies looking at risk of transmission via sexual contact, and its correlation
with viral load and ART treatment status. Findings were published in the April
17, 2009 advance online edition of AIDS; results were previously presented in
part at the XVII
International AIDS Conference last August in Mexico City The
investigators searched the Medline and Embase medical literature databases and
conference abstracts from 1996 through 2009, looking for longitudinal studies
of serodiscordant couples reporting rates of HIV transmission according to plasma
viral load and/or use of ART. They used random-effects Poisson regression models
to obtain summary transmission rates. If a study observed no transmission events,
the authors estimated an upper 97.5% confidence limit. Results
The investigators identified studies of 11 relevant cohorts, representing a total
of 5021 heterosexual couples.
A total of 461 HIV transmission events were reported in these studies.
The overall rate of HIV transmission from individuals on ART was 0.46 per 100
person-years, based on 5 events.
The transmission rate from an HIV positive partner on ART with viral load below
400 copies/mL was zero, based on 2 studies, with 1.27 per 100 person-years as
the upper limit of the estimated range.
The estimated transmission rate was 0.16 per 100 person-years if the HIV positive
person is not on ART, based on 5 studies and 1 event.
There were not sufficient data to calculate transmission rates according to the
presence or absence of sexually transmitted infections, condom use, or vaginal
versus anal intercourse.
"Studies
of heterosexual discordant couples observed no transmission in patients treated
with ART and with viral load below 400 copies/mL, but data were compatible with
one transmission per 79 person-years," the study authors concluded. "Further
studies are needed to better define the risk of HIV transmission from patients
on ART."
These findings indicate that while the risk of transmission
is very low when an HIV positive person is on effective ART -- and treatment can
certainly help lower the transmission rate on a community or population level
-- there is no guarantee against transmission in any individual case.
Institute
of Social and Preventive Medicine (ISPM), University of Bern, Switzerland; Department
of Social Medicine, University of Bristol, UK.
5/08/09 Reference
S
Attia, M Egger, M Müller, and others. Sexual transmission of HIV according
to viral load and antiretroviral therapy: systematic review and meta-analysis.
AIDS. April 17, 2009 [Epub ahead of print]. (Abstract).
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