title: The increasing marginal benefit of condom usage.
abstract: OBJECTIVE
  Condom use is promoted as a primary strategy for preventing sexual transmission of human immunodeficiency virus (HIV). This paper analyzes how incremental changes in condom compliance rates can affect an individual's risk of acquiring HIV.
  
  
  METHODS
  We developed a simple mathematical model of HIV transmission in which the cumulative probability of HIV infection depended in part upon the percentage of acts in which a condom was used. We applied basic methods of calculus to differentiate the mathematical model with respect to the probability of condom usage. We applied values from published studies to the model to illustrate how the marginal benefits of condom usage vary across different populations.
  
  
  RESULTS
  In general, the marginal benefit of condom usage increases as condom compliance increases.
  
  
  CONCLUSIONS
  The marginal benefits of increased condom usage vary across different risk groups and across different levels of condom compliance. These results offer insight into the motivation behind the decision of whether or not to use condoms, and indicate possible ways to optimize the use of resources devoted to increasing condom usage by at-risk populations.
authors.affiliation: Division of STD Prevention, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA.
authors.forename: H W
authors.initials: HW
authors.lastname: Chesson
authors.forename: T L
authors.initials: TL
authors.lastname: Gift
mesh_terms: D017280:Condoms / Q000706:statistics & numerical data*; D018562:Disease Transmission, Infectious / Q000517:prevention & control*; D005260:Female; D015658:HIV Infections / Q000517:prevention & control* / Q000635:transmission; D006801:Humans; D008297:Male; D008962:Models, Theoretical; D010349:Patient Compliance / Q000706:statistics & numerical data; D010353:Patient Education as Topic; D011336:Probability; D018570:Risk Assessment