HIV treatment as prevention: the experience in British Columbia

Michael Carter
Published: 19 February 2014

Expanded coverage of HIV therapy in British Columbia has been accompanied by a 42% reduction in HIV incidence and 80% reductions in the incidence of both AIDS and HIV-related mortality, investigators report in PLOS ONE.

“Our results show that HAART [highly active antiretroviral therapy] expansion in BC [British Columbia] between 1996 and 2012 was strongly and statistically significantly associated with sustained population-level decreases in HIV/AIDS related morbidity and mortality, as well as concomitant decreases in new HIV diagnoses, and estimated HIV incidence,” comment the investigators. “Expansion of HAART coverage was also associated with increased adherence rates, increased rates of viral suppression, and decreased rates of HIV resistance.”

Thanks to improvements in antiretroviral treatment, most people living with HIV in resource-rich settings now have a normal or near-normal life expectancy. HIV therapy also has public health benefits, as treatment that suppresses viral load to undetectable levels is associated with a near-zero risk of transmission to sexual partners.

There have therefore been calls for the scale-up of antiretroviral therapy, with the use of HIV treatment as prevention.

Data collected in British Columbia, Canada, are capable of providing real-world population-level evidence of the effectiveness and sustainability of such a strategy.

Investigators used information collected by province-wide registries between 1996 and 2012 to examine trends in the use of HIV therapy, viral load, CD4 cell count, the incidence of AIDS and HIV-related mortality, the annual number of new HIV diagnoses and HIV incidence.

HIV prevalence in the province increased from 7900 cases in January 1996 to 11,972 cases in January 2012, a statistically significant 52% increase (p < 0.001). Over the same period, the number of people taking potent HIV therapy increased from 837 to 6772 (709%; p < 0.001). The estimated proportion of HIV-positive patients taking treatment therefore increased from 11 to 57% (p = 0.0004) during the study period.

There were 253 AIDS deaths in 1996 and 59 AIDS deaths in 2011. The HIV-related mortality rate fell from 6.5 to 1.3 per 100,000 during 1996-2011 – an 80% decrease (p = 0.0115). The rate of AIDS diagnoses fell from 6.9 to 1.4 per 100,000 – also representing an 80% decrease (p = 0.0330).

Baseline CD4 cell count at the initiation of HIV therapy increased from a median of 270 cells/mm3 to 380 cells/mm3 (p < 0.001). The proportion of patients with optimal levels of adherence (95% and above) increased from 37% in 1996 to 71% by 2012 (p = 0.032).

Using 500 copies/ml as the cut-off, the proportion of treated patients with virological suppression increased from 8 to 74% between 1996 and 2012 (p < 0.001). When the more stringent value of 50 copies/ml was used, the proportion of people with suppressed viral load increased from 6 to 59% (p < 0.001).

The prevalence of drug resistance decreased during the study period from 85 to 31% (p < 0.001).

There was a steady decrease in the number of new HIV diagnoses, from 702 cases in 1996 to 238 cases in 2012, a significant 66% reduction (p = 0.004).

HIV incidence fell from an estimated 632 cases per year to 368 cases per year, a 42% fall (p = 0.013).

Each 100 individuals on HIV therapy decreased HIV incidence by an estimated 1.2% and each 1% increase in the proportion of treated patients with viral suppression decreased HIV incidence by 1%.

“Our results support the long-term population-level effectiveness and sustainability of the treatment as prevention strategy,” comment the authors. “It is reassuring to note that evidence in support of a population-based impact of treatment on the prevention of HIV transmission continues to emerge in diverse global settings. Such effects have been described in Taiwan, and more recently in Vancouver, Baltimore, San Francisco, China and KwaZulu-Natal.”