Second British Columbia paper, 2008

The previous two models produced relatively little reaction at the time. A second paper published by the same team two years later¹ convinced the British Columbia Health Minister to adopt a policy of expanding use of antiretroviral therapy in order to curb new HIV infections in the province.

Montaner’s team’s second paper restricted itself to British Columbia, in order to use better data and produce more precise predictions. It calculated that expanded use of antiretroviral therapy (accompanied by good adherence) had the potential to avert two-thirds of new HIV infections in the province by 2030. This would be the case if all individuals eligible for antiretroviral therapy started such treatment when their CD4 cell count was in the region of 350 cells/mm³- the current recommended threshold for initiating anti-HIV treatment in the UK.

At the time of the analysis only 50% of HIV-positive individuals in British Columbia started antiretroviral therapy before their CD4 cell count fell to below 200 cells/mm³, and patients on treatment took approximately 78% of their doses – well below the 95% target and at the level which involves the greatest risk for the development of drug-resistant virus.

The investigators calculated that this level of treatment coverage and adherence would lead to a modest increase in the annual number of new HIV infections every year – from 421 in 2006 to 462 in 2030.

They then calculated the potential impact of more patients starting anti-HIV treatment before their CD4 cell count fell to the 200 cells/mm³ threshold. Their calculations showed that if 75% of eligible patients had started treatment by this stage it would yield a 37% reduction in the total number of new HIV infections, and if 100% of patients had started treatment before they reached a CD4 cell count of 200 cells/mm³, then 62% of onward transmissions would be averted.

If 75% of patients started treatment when their CD4 cell count was 350 cells/mm³, then 40% of the projected new infections by 2030 would be averted, and this would increase to 67% of anticipated infections if all patients started treatment when their CD4 cell count was around 350 cells/mm³. Increasing patient adherence would further modestly increase the number of averted infections.

Faster expansion of anti-HIV treatment would result in faster decreases in the numbers of new infections, according to the investigators' model. Furthermore, immediate expansion of access to anti-HIV treatment would save a total of Canadian $95 million, or Canadian $368,000 per patient. 

“Our results indicate that higher HAART coverage consistently leads to a decrease in the number of individuals testing newly positive for HIV”, Montaner wrote. “Expansion of HAART coverage should lead to a substantial reduction of the growth of the HIV epidemic and related direct treatment costs. Our model supports a powerful and as-of-yet little appreciated additive preventative value for expanding HAART coverage.”

Three days after this model was published, British Columbia’s Health Minister, George Abbott, announced that the province would implement a new, aggressive strategy to expand antiretroviral coverage in order to curb new HIV infections. In a press article on the strategy,² Professor Montaner said: "The more people you treat, and the faster you engage people in treatment, the greater impact you will have on the epidemic."

George Abbott told the paper: "This would be leading-edge from a global perspective, not just a Canadian perspective."

It was estimated that up to 15,000 individuals are infected with HIV in British Columbia, of whom 27% were thought to be unaware of their infection. However, as of May 2008, just 4379 were on ART even though all drugs were available in the province free of charge. The majority of individuals who had not taken up ART, despite being eligible, were thought to be people on low incomes, aboriginal Canadians living in remote communities, as well as HIV-positive, injecting drug users, some of whom were also homeless and/or mentally ill.

Both Professor Montaner and Minister Abbott admitted that expanding ART to these populations would be difficult, and the new strategy might include paying individuals to take their treatment as prescribed.

Although the programme will be costly in the short-term, the British Columbia Health Minister noted: "It's far more cost-effective to prevent disease than it is to treat disease.”

Full implementation of the project began in February 2010, and a series of pilot projects will run until 2013.³