A mathematical model has shown that just under half of countries in sub-Saharan Africa are likely to reach UNAIDS’ ambitious 90-90-90 target and ultimately 73% of all people living with HIV in this region are predicted to be virally suppressed by 2020, researchers report in the November issue of Tropical Medicine and International Health.
The UNAIDS 90-90-90 target states that by 2020, 90% of people living with HIV should be diagnosed, 90% of those diagnosed treated, and 90% of those treated virally suppressed. The ultimate aim of this ambitious target is to end the AIDS epidemic by 2030.
While the model predicts that 19 countries will reach the first two UNAIDS targets if they maintain current rates of treatment initiation, 15 countries would require a multiple-fold increase in the annual number of people starting antiretroviral therapy (ART). Most of these are located in west and central Africa.
The authors input country-specific data on numbers of people infected, diagnosed and treated into their model. The model simulated the progression of HIV from ART initiation onwards, assuming a treatment failure rate of 6% one year after and 13% five years after starting ART.
The model assessed the number of people needing to start ART from 2017 to 2020 to achieve 81% treatment coverage by 2020 in each country.
The model projected that 2.9 million people started ART in 2017 in sub-Saharan Africa. Moreover, if at least 2.2-2.7 million people continue to start ART annually, 81% ART coverage will be reached in 2020.
However, countries vary in the treatment scale-up that is required to meet the UNAIDS targets. Of the 41 assessed countries, 19 (46%) can reach the first two targets by keeping the number of people who start ART at 2017 levels. In seven countries (17%), the ART initiation rate needs to be moderately scaled up, up to doubling the number of people starting ART annually.
In 15 countries (37%) – most of these in West and Central Africa – a more substantial increase is needed. The situation is most critical in Liberia, Madagascar, Mauritania and South Sudan, requiring more than a tenfold increase.
The authors then considered four scenarios, in order to better understand the impact of virological monitoring and retention on outcomes. This shows that virological suppression greater than 90% in 2020 could be reached only in a best-case scenario assuming low probability of treatment failure, elimination of treatment interruptions, and universal routine viral load monitoring.
In an optimal scenario in which there are no treatment interruptions, viral load monitoring occurs annually, and individuals would immediately switch to a second-line regimen, 94.2% of people would be virally suppressed.
That scenario was modified so that CD4 cell counts were monitored annually and viral load testing was only used to confirm treatment failure, but the conditions were otherwise the same. In this scenario, 89.8% would be virally suppressed.
The researchers then considered the current scenario, without improvements in retention and switching. Combining this with universal routine viral load monitoring is predicted to result in 83.7% being virally suppressed.
Modifying the last scenario so that viral load testing was only offered after the CD4 cell count suggested treatment failure resulted in 81.0% being virally suppressed.
The researchers then considered an alternative analysis that focused on nine countries (Benin, Cameroon, Gabon, Lesotho, Liberia, Madagascar, Mali, Niger, and Uganda) with current viral suppression rates that are below 70%. Moreover, whereas the first analysis assumed a treatment failure rate of 6% after one year and 13% after five years, this second analysis assumed higher failure rates of 26% and 51% respectively.
Results varied in the four scenarios – viral suppression would be achieved by 76.9%, 64.0%, 60.0% and 51.6% respectively.
The study had several limitations – it was not a transmission model and didn’t predict the development of the HIV epidemic. As such, it did not consider the potential influence of improved viral suppression on incidence, mortality, and prevalence.
Coverage estimates for 2020 were based on the assumption that the number of people living with HIV will stay approximately stable in the future – improvements in life expectancy would be offset by fewer new infections.
The model used the same parameter values for all countries with the exception of the ART initiation rate, therefore could not catch all the differences between countries.“The model is therefore likely to be well applicable to many settings in southern Africa, but not to settings facing serious problems in keeping viral suppression,” comment the authors.
The authors say that their model shows that the 90-90-90 target is realistic in sub-Saharan Africa “on average”, but not necessarily in each individual country. They advise that each country should identify and focus on the specific gaps needing attention – from testing, diagnosis, linkage to care, ART initiation, and adequate retention and adherence, to sustained and virally suppressive ART.
Several high-prevalence countries in east and southern Africa have reached a high level of ART coverage. Their challenges are to maximise viral suppression and retention by improving laboratory monitoring and counselling during treatment, implement differentiated service delivery models, and establish access to improved treatment options.
However, in several countries of west and central Africa, a massive increase in the number of people enrolling on ART is needed. The main gap is from infection to diagnosis, suggesting that substantial investments are needed to identify undiagnosed individuals.
One major reason for the differences between countries is likely the differing nature of the epidemic. In east and southern Africa, the epidemic is generalised, and patients are predominantly young women who are easier to reach through antenatal care. Due to the high prevalence, HIV has been a national priority.
On the other hand, in west and central Africa, overall prevalence is lower, and people living with HIV are more concentrated amongst population groups who are marginalised and may face stigma and whose behaviour may be criminalised.
The authors suggest that in order to achieve 90% viral suppression amongst those on ART, countries must combine multiple interventions, including improvements in monitoring, switching and retention. They call for routine viral load monitoring and prompt switching to a second-line regimen immediately in case of treatment failure.
Achieving the 90-90-90 target will continue to require investments across the cascade of care and priorities will differ by country and region, the authors say. Some countries are close to the target and these should focus on improving retention and viral suppression whereas for others, a substantial increase in the scale-up of ART is needed. Each country should identify and focus on the specific gaps needing attention.
By Esther Nakkazi, Roger Pebody
Estill J et al. How to achieve the global 90‐90‐90 target by 2020 in sub‐Saharan Africa? A mathematical modelling study. Tropical Medicine and International Health 23:1223-1230, 2018. (Abstract).