The researchers stress, however, that any successful HIV vaccination effort should include a behavior-modification program in order to prevent increases in risky behavior after vaccination. Both of the new studies modeled a range of theoretical scenarios and vaccines. The study population consisted of approximately 50,000 gay men in San Francisco, and assumptions regarding this population were based on data from actual surveys and other studies. She is a senior member of the technical staff in the Systems Research Department at Sandia National Laboratories. Ross Shachter, an associate professor in the Department of Engineering-Economic Systems and Operations Research, guided the mathematical modeling on the projects as Edwards' dissertation adviser.
Preventive vaccines aim to prevent new infections by inducing immunity in uninfected individuals.
Therapeutic vaccines are given to individuals who are already infected, in an attempt to rouse the immune system to fight the virus. In the Interfaces study, the benefit from an imperfect vaccine was particularly noticeable in the case of a preventive vaccine. The vaccine appeared most beneficial resulting in a gain in healthy years as well as a decrease in health care costs when efficacy was 75 percent or more and protection lasted at least 10 years, or when efficacy was at least 50 percent with lifetime protection. But for the preventive vaccine, there were greater benefits for a given expenditure and the vaccine more often resulted in savings both in healthy years and in health care expenses. This makes sense, said Owens, because the uninfected target population for the preventive vaccine is much larger in an early-stage epidemic.