Treating All HIV Positive People According to Current Guidelines Could Dramatically Reduce New Infections

By Liz Highleyman

Adult and Adolescent Guidelines

Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents - January 29, 2008

Recent setbacks in the field of HIV prevention, including failed studies of vaccines and herpes treatment, have led researchers to seek more effective strategies.

One potential approach is expanding access to antiretroviral drugs, since people taking combination anti-HIV therapy typically achieve decreased -- or, ideally, undetectable -- viral load, which dramatically lowers the chances of transmitting the virus to others.

As reported in the July 1, 2008 Journal of Infectious Diseases, Julio Montaner of the British Columbia Centre for Excellence in HIV/AIDS in Vancouver, Canada, and colleagues constructed a mathematical model to explore the effect of greater HAART coverage on the number of incident HIV infections in British Columbia over the next 25 years.

Montaner's team previously estimated that treating all HIV positive people within 1 year after infection might reduce transmission by as much as 70 percent. This suggestion was controversial, however, due to the ethical and financial drawbacks of exposing people to drug-induced toxicities before they need treatment, promoting more rapid emergence of drug resistance, and diverting drugs for prevention purposes when many so many people worldwide are still in dire need of treatment.

In the present analysis, Montaner and colleagues focused on HIV positive people who require treatment themselves - that is, those whose CD4 cell count has fallen to the 350 cells/mm3 threshold for treatment initiation specified in the latest U.S. and European antiretroviral therapy guidelines.

The researchers looked at different scenarios involving varying assumptions regarding degrees of drug resistance, adherence to therapy, initiation thresholds, HAART coverage, and timing of HAART uptake. (Currently, it is estimated that only about half of HIV positive people in British Columbia start antiretroviral therapy before their CD4 cell count falls below 200 cells/mm3.)

If all medically eligible individuals started antiretroviral therapy at the 350 cells/mm3 threshold and maintained good adherence, the study authors calculated, about two-thirds of new infections might be averted by the year 2030. If 75% started therapy at this threshold, HIV incidence would still decrease by nearly 40%.

In addition, they calculated that at today's prices, this degree of expanded treatment coverage would be cost-effective, saving a total of about $95 million.
In conclusion, the researchers wrote, expanded antiretroviral therapy could lead to "substantial reductions in the growth of the HIV epidemic and related costs." These results, they added, "provide powerful additional motivation to accelerate the roll out of HAART programs aggressively targeting those in medical need, both for their own benefit and as a means of decreasing new HIV infections."

Commentary

In a related commentary in the July 1, 2008 Canadian Medical Association Journal, Aranka Anema, Evan Wood, and Montaner expanded on their proposal for expanded use of HAART to reduce HIV incidence at the population level.

The authors argued that this approach has been "overlooked as a viable public health strategy" for reducing the number of new HIV infections, even though it is an accepted component of public health efforts to prevent transmission of other infections such as tuberculosis, syphilis, and genital herpes.

It is already widely acknowledged that antiretroviral therapy plays in major role in preventing mother-to-child HIV transmission during pregnancy and delivery, and it is considered the standard of care used if the woman does not yet need treatment herself.

Further, some observational studies in both industrialized and resource-limited countries have shown that reduction in viral load - in both blood and genital fluids -- due to therapy is associated with reduced risk of transmission between serodiscordant couples. On a population level, the authors noted, new HIV diagnoses fell by about 50% in both Canada and Taiwan after the introduction of easily accessible or free antiretroviral therapy, despite similar sexual risk behavior (as assessed based on continued increases in syphilis rates).

"Expanded access to highly active antiretroviral therapy for patients with a medical indication will reduce AIDS-related morbidity and mortality and may reduce HIV incidence," the authors concluded. "There is a need to prospectively validate and quantify the preventive impact of highly active antiretroviral therapy on the incidence of HIV at the population level."

7/04/08

References

VD Lima, K Johnston, RS Hogg, JSG Montaner, and others. Expanded access to highly active antiretroviral therapy: a potentially powerful strategy to curb the growth of the HIV epidemic. Journal of Infectious Diseases 198(1): 59-67. July 1, 2008. [ Abstract ]

A Anema, E Wood, and JSG Montaner. The use of highly active retroviral therapy to reduce HIV incidence at the population level. Canadian Medical Association Journal. 179 (1): 13-14. July 1, 2008.