Combination prevention could "eliminate" HIV transmissions in Vietnam, model projects

A “combination prevention” strategy with targeted HIV testing and early antiretroviral therapy at its core has the potential to virtually eliminate new HIV transmissions in Vietnam, according to a mathematical model published in the online edition of the Journal of Acquired Immune Deficiency Syndromes. The strategy had the biggest impact on transmissions and was most cost-effective when it was targeted at high-risk populations.

“Active HIV case finding and earlier access to ART [antiretroviral therapy] for key populations combined with other interventions could lead to highly effective and cost-effective reductions in HIV transmission in this concentrated epidemic setting,” write the authors. “Projections using this strategy suggest that it would dramatically reduce HIV incidence to 1/100,000 in 14 years, and achieve annual cost saving after around 20 years.”

There is considerable interest in the use of antiretroviral therapy as prevention. Mathematical models have shown that, in some scenarios, expanded testing and immediate antiretroviral therapy could theoretically halt the HIV epidemic in high-prevalence settings such as South Africa.

An international team of investigators wanted to assess the potential impact of expanded use of antiretroviral treatment as prevention in Vietnam.

Like many Asian countries, the Vietnamese HIV epidemic is concentrated in high-risk groups, especially people who inject drugs, as well as female sex workers and men who have sex with men.

In total, approximately 249,000 people are living with HIV, of whom 61,000 are receiving antiretroviral therapy. There is already good coverage of needle and syringe programmes.

The researchers developed a model based on HIV prevalence trends in Can Tho province. They modelled the future course of the epidemic until 2050 according to several scenarios including:

• Use of antiretroviral therapy, HIV testing and other prevention interventions are maintained at 2010 levels.

• All adults receive annual HIV tests with people testing positive receiving immediate HIV therapy. Other interventions remain at 2010 levels.

• All members of specific high-risk groups receive annual HIV tests and immediate HIV therapy if necessary. Populations examined separately included people injecting drugs, men who have sex with men, female sex workers, and their male clients.

• Testing and immediate therapy for several high-risk groups, combined with methadone maintenance therapy for injecting drug users and efforts to increase condom use in high-risk groups ("combination prevention").

It's worth noting that the model assumes that all members of a population can be reached by healthcare staff and accept the offer of an HIV test. The model also assumes that antiretroviral therapy can be provided to everybody with diagnosed HIV.

Results of the model showed that, if antiretroviral coverage and prevention efforts were maintained at current levels, there would be 18,115 new HIV infections and 7624 deaths within the province by 2050, at a cumulative cost of US$22.1 million.

Universal annual testing and immediate HIV therapy would reduce the number of new infections by 80% and also avert 78% of deaths. But this would be at the cost of tripling the budget for HIV treatment and testing.

Annual testing and immediate treatment targeted at injecting drug users would achieve a 75% reduction in the number of new diagnoses and avert 69% of projected deaths. The estimated costs were 7% higher than those associated with maintaining current treatment levels and prevention coverage.

If the target groups were female sex workers, their clients, or men who have sex with men, then new infections would be reduced by 31, 25 or 19% respectively, and the number of AIDS-related deaths would be reduced by between 27 and 36%. The estimated costs were 19 and 23% higher when testing sex workers and MSM respectively, but 53% higher if the larger group of male clients of sex workers needed to be tested.

However, the investigators’ model showed that the most promising strategy was the combination prevention approach. Providing testing and treatment for injecting drug users, female sex workers and men who have sex with men, combined with methadone maintenance therapy and substantial increases in condom use, would reduce the number of new infections by 81%, preventing almost three-quarters of AIDS-related deaths. The estimated cost was $22.7 million, only 3% more than that associated with maintaining the status quo.

Moreover, the combination prevention approach was projected to reduce HIV incidence in the province from the current level of 61 per 100,000 person-years to less than 1 per 100,000 person-years by 2024, effectively eliminating the epidemic.

Although there would be substantial upfront costs, the combination approach would be cost-saving after 2028.

“The best strategy consisted of delivering services to key populations including early HIV diagnosis, immediate ART, MMT [methadone maintenance therapy], condom use alongside the current approach,” comment the investigators.

They conclude, “targeted and frequent HTC [HIV testing and counselling] and earlier ART significantly decreases HIV infections and deaths, and when combined with other interventions, it could make a substantial contribution to the earlier achievement of HIV control and elimination.”