The roll-out of
antiretroviral therapy (ART) in South Africa has achieved “astounding” results,
a mathematical model published in the online edition of the Journal of Infectious Diseases shows.
Each person who started HIV therapy between 2004 and 2011 had an individual
gain in life expectancy of 11 to 13 years. The estimated population
lifetime survival benefit for all people initiating ART in this period was 21.7
million life-years. Increasing the number of people linked to care and
expanded access to second-line therapies could increase the gain to 36 million
contributes to a growing literature establishing the profound survival benefits
resulting from investments in the global response to the HIV pandemic,” write
In an editorial
accompanying the study, Sten H Vermund of the Institute for Global Health at
Vanderbilt University said: “The magnitude of the benefit of South African
ART-based programs is astounding.”
There are an
estimated 5.6 million people living with HIV in South Africa, more than in any other
country. Approximately 2.8 million people qualify for ART. However, despite
the roll-out of treatment, a third of people eligible for therapy are not
team of investigators wanted to quantify the cumulative survival benefit
attributable to ART since its introduction in South Africa in 2004.
They used the
Cost-Effectiveness of Preventing AIDS Complications-International model of HIV
disease and treatment (CEPAC) to simulate and model the impact of ART roll-out
in people starting ART between 2004 and 2011.
The simulation was
based on data collected by the South African Catholic Bishops Conference, and
estimated that patients had a mean age of 37 years and 33% were men. It was also
estimated that mean CD4 cell count at the time of ART initiation ranged between
112 and 178 cells/mm3 and 46% of patients had a baseline viral load
above 100,000 copies/ml. ART was assumed to achieve a reduction in AIDS-related
mortality of between 56 and 96%. An estimated 78% of patients were assumed to
have an undetectable viral load six months after initiating ART and the CD4
cell gain from baseline at this time was 148 cells/mm3. The modelled
scenario also assumed that only 2.4% of patients had access to second-line ART
and that the rate of retention in care at month 36 was between 55 and 71%.
Additional data were also entered into the model to simulate the impact of ART
should access to treatment and linkage to care improve.
The model was used
to simulate survival for the cohort twice – first assuming no ART and then with
The number of
patients initiating ART each year grew from 50,000 in 2004 to 557,000 in 2011.
By 2011, a total of 2,222,700 individuals had started HIV therapy.
Without ART, people had an estimated individual life expectancy of approximately two
years. This increased to approximately 11 to 13 years with ART.
Overall, a total
of 17.9 life-years would be saved with current ART policies, increasing to 21.7
million life-years with universal second-line ART, 23.3 million life-years with
increased linkage to care for eligible but untreated patients and 28 million
life-years with both improved linkage to care and universal second-line
therapy. The most optimistic scenario involved a survival benefit of
approximately 36 million life-years.
“We provided a
model-based estimate of the survival benefits attributable to ART in South
Africa,” write the authors. “In the base case, 21.7 million life-years were
attributable to ART over the lifetime of all persons initiating ART during
2004-11, of which only 2.8 million life-years (12.7%) has been realized as of
December 2012. Implementation of expanded testing and treatment policies…were
projected to significantly increase these benefits.”
The author of the editorial
stresses the investigators’ model was based on “data-driven assumptions with
robust simulations…the assumptions were based on real-world programmatic
information, not theoretical benefits of more-idealized programs.”