How can we calculate the E in CEA?Bollinger, Lori AAIDS: July 2008 - Volume 22 - Issue - p S51–S57 doi: 10.1097/01.aids.0000327623.31856.45 Section I: Informing Scale-up and Resource Allocation Abstract Author Information Because full funding for HIV/AIDS prevention interventions is unlikely to occur in the near future, it is essential that the resources available are spent in the most effective way possible. This paper presents a matrix of effectiveness coefficients for HIV/AIDS-related prevention interventions that can be used as an integral part of the coordinated strategic planning process currently underway by the World Bank and UNAIDS, as the interventions in the matrix are harmonized with the interventions in that process. Coefficients for four types of sexual behavior change (condom use, partner reduction, sexually transmitted infection treatment-seeking behavior, age at first sex) across three different risk groups (high, medium, low) are presented, along with their interquartile ranges. Results indicate that: (1) impacts seem greater when an intervention includes interpersonal contact, rather than targeting a more general audience; (2) although significant impacts are observed in the columns measuring changing condom use, other impacts are lower, and sometimes are actually (measured) zero; and (3) additional studies have evaluations of the number of sexual partners and have found a greater impact than previous studies. Although progress has been made in increasing the number of evaluation studies that can be utilized in this impact matrix, particularly in the area of youth interventions, there are still empty cells in which no studies report impacts. Finally, it is important to note that issues such as quality differences and synergies between programmes could have an effect on the impacts calculated for a particular strategic plan. From the Futures Institute, Glastonbury, Connecticut, USA. Correspondence to Lori A. Bollinger, Futures Institute, 41-A New London Turnpike, Glastonbury, CT 06033, USA. E-mail: LBollinger@FuturesInstitute.org © 2008 Lippincott Williams & Wilkins, Inc.