Jump to comment:

• Higher-than-85% condom use rate in persons with multiple sexual partners is required to control HIV
  Chi-Tai Fang
  Published on: 25 November 2005

• Published on: 25 November 2005

  Higher-than-85% condom use rate in persons with multiple sexual partners is required to control HIV

  • Chi-Tai Fang, Doctor
  • Other Contributors:
    • Yu-Yin Chang and Jung-Der Wang

  Dear Editor,

  We read with interest the paper by Brown and Peerapatanapokin regarding estimated condom use rate required to control the HIV epidemic in Thailand.[1] Their Asian Epidemic Model predicts that a sustained high condom use rate (85% or more) among sexual workers is required to control the HIV epidemic. If the condom use rate drops to 60%, their model predicts a resurgence of the HIV epidemic.[1] We reac...

  Show More

  Dear Editor,

  We read with interest the paper by Brown and Peerapatanapokin regarding estimated condom use rate required to control the HIV epidemic in Thailand.[1] Their Asian Epidemic Model predicts that a sustained high condom use rate (85% or more) among sexual workers is required to control the HIV epidemic. If the condom use rate drops to 60%, their model predicts a resurgence of the HIV epidemic.[1] We reached a similar conclusion using a different model developed for a different situation in Taiwan[2], where prevalence of HIV infection is as low as 0.019% (end of 2002) and highly active antiretroviral therapy has been freely provided by the government since 1997.

  Sexual contact (96.4%, n=4,390 at the end of 2002) has been the predominant risk factor for acquiring HIV infection in Taiwan.[2] Because HIV prevalence is extremely low, evolution of the HIV epidemic in Taiwan can be approximated by a simple exponential model defined by the equation: dN(t)/dt = R*N(t) - m*N(t), where N(t) is the number of patients with HIV infection at time t, R is the average transmission rate (new cases per prevalent case per year) and m is the risk of mortality (deaths per prevalent case per year). The magnitude of the HIV epidemic will decrease only if R < m.

  Using our previously published estimates for R and m values in Taiwan (R=0.184 and m=0.046 per prevalent case-year, 1998-2002, respectively)[2], plus the assumption that the value R=0.184 is under the scenario of 10% condom use with 90% protection efficacy among sexually active persons with multiple partners, the condom use rate level which is required to control HIV epidemic can be calculated as below:

  Hypothetical R under 0% condom use scenario = 0.184/(1-(10%)*(90%)) = 0.202

  Hypothetical R under x % condom use scenario = 0.202*(1-(x%)*(90%))

  Solve the x% when R = m = 0.046; we get x% = 85.8%

  In another words, the condom use rate must be increased to 86% in order to turn the tide of the sexually transmitted HIV epidemic. Sensitivity analysis to assume baseline condom use rates of 5%, 15%, and 45% only shifts the required condom use rates for HIV control to 85%, 87%, and 95%, accordingly. Thus, an equally high rate of condom use among sexually active persons with multiple partners is required to control the HIV epidemic in a low prevalence area like Taiwan in this era of highly active antiretroviral therapy.

  Chi-Tai Fang,¹ Yu-Yin Chang,² Jung-Der Wang^1,2

  ¹ Department of Internal Medicine, National Taiwan University Hospital
  ²College of Public Health, National Taiwan University.

  We declared no competing interests.

  References:

  1.Brown T, Peerapatanapokin W. The Asian Epidemic Model: a process model for exploring HIV policy and programme alternatives in Asia. Sex Transm Infect 2004; 80 (Suppl 1): 19-24.

  2.Fang CT, Hsu SM, Twu SJ, et al. Decreased HIV transmission after a policy of providing free access to highly active antiretroviral therapy in Taiwan. J Infect Dis 2004; 190: 879-885.

  Show Less

  Conflict of Interest:
  None declared.

  • Back to top