Background: Developing countries can anticipate that HIV vaccine quantities will be initially constrained by manufacturing production capacities, making the determination of optimal HIV vaccination policies crucial. Because the roles of various risk groups (e.g., commercial sex workers (CSWs), intra-venous drug users (IVDUs), etc.) in the epidemiology of HIV transmission can differ dramatically among developing countries, it is important that each country develop sound strategies to ensure that their limited HIV vaccine resources are optimally deployed. Objective: To demonstrate that indirect vaccine effects (i.e., vaccine effects protecting unvaccinated individuals via herd immunity, or vaccine effects reducing the infectiousness of those infected despite vaccination) could substantially outweigh direct vaccine effects in a number of epidemic scenarios for developing countries. Methods: A deterministic mathematical model consisting of a nonlinear system of differential equations was used to model the HIV epidemics. A computer simulation system was constructed to implement this model for several HIV epidemic scenarios. Results: When vaccine availability is limited relative to the general population size, the reductions in HIV transmission due to indirect vaccine effects greatly exceeded reductions due to direct effects under optimal vaccine distribution conditions in several simulation scenarios. Conclusions: Considering the impact of indirect vaccine effects when determining optimal HIV vaccine distribution policies will be beneficial to HIV vaccination policy and planning in developing countries.
Learning Objectives: At the conclusion of the session, the participant (learner) in this session will be able to: 1) Distinguish between direct and indirect vaccine effects. 2) Articulate why vaccine availability contraints often cause indirect effects to predominate over direct effects under optimal vaccine distribution conditions. 3)Appreciate the importance of considering indirect vaccine effects when evaluating vaccine distribution policies.
Keywords: HIV/AIDS, Immunizations
Presenting author's disclosure statement:
Organization/institution whose products or services will be discussed: None
I do not have any significant financial interest/arrangement or affiliation with any organization/institution whose products or services are being discussed in this session.