The provision of free HAART decreased HIV transmission by 53% in Taiwan, according to an article published in the Septmber 1st edition of The Journal of Infectious Diseases (now available on-line). The Taiwanese investigators caution however, that proving anti-HIV therapy is not enough on its own to prevent the spread of HIV. They note that thousands of new syphilis cases a year suggest that there is widespread sexual risk taking, and that efforts must continue to promote condom use.
It has been suggested that the widespread use of HAART could lead to a population-wide reduction in HIV transmission. However, there are little empirical data to support this theory, partly because the cost of HAART prevents its use in many countries and because few countries have in place surveillance systems able to accurately track the incidence of new HIV infections.
A possible negative impact which could arise from the widespread use of HAART could be an increase in sexual risk taking because of optimism about HAART. A recently published meta-analysis of studies looking at this question found that individuals who believed that a low viral load made people with HIV less infectious were likely to take more sexual risks. Furthermore, mathematical models suggest that even a modest increase in unsafe sexual activity has the potential to offset a large decrease in infectiousness brought about by the widespread use of HAART.
Taiwan has had in place a national HIV surveillance programme since 1989, and since 1997 had provided HIV-positive individuals with access to free triple drug antiretroviral therapy according to US guidelines. This provided investigators with an opportunity to construct a mathematical model to determine the effect of widespread use of HAART on the evolution of the HIV epidemic. To differentiate the effects of HAART on HIV transmission from the effects of behavioural change, investigators also gathered data on the incidence of syphilis in both the general population and amongst individuals with HIV.
Between 1984 and 2002 a total of 4390 HIV cases were recorded in Taiwan. The majority of these cases involved gay men (54%), but the investigators speculate that gay men may make up an even larger proportion of individuals living with HIV in Taiwan because strong cultural taboos make it difficult for many men to be open about their sexual behaviour. They believe that few cases of HIV are due to injecting drug use in Taiwan due to the ready availability of clean needles.
After HAART became freely available, the investigators’ linear regression model suggested that the HIV transmission rate fell by 53%, a statistically significant drop (p = 0.005).
That this fall in HIV transmission was due to HAART rather than behavioural change was demonstrated when the investigators looked at the incidence of syphilis in both the pre- and post-HAART era. There was no statistically significant reduction in cases of new syphilis in either the general population, or amongst HIV-positive individuals (p = 0.53).
“Our research shows that, after implementing a policy of providing free access to HAART to all HIV-infected citizens, the HIV transmission rate decreased by 53% in Taiwan. This result makes a strong case for the more widespread use of HAART as a control measure against the HIV and AIDS epidemics in countries with low prevalence.”
However, the investigators caution that the prevention gains which HAART has brought could be quickly lost if efforts are not made to promote condom use, as the incidence of sexually transmitted infections shows that unsafe sex is widely practiced.
Fang C-T et al. Decreased HIV transmission after a policy of providing free access to highly active antiretroviral therapy in Taiwan. J Infect Dis (online edition) 190, 2004.