HIV Vaccine Preparedness Studies in the Organization for Economic Cooperation and Development OECD Countries A Systematic Review.

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Slide 1 : HIV Vaccine Preparedness Studies in the Organization for Economic Co-operation and Development (OECD) Countries: A SYSTEMATIC REVIEW Slides by: Dr. Shayesta Dhalla and Dr. Gary Poole, June 2008. School of Population and Public Health, University of British Columbia, Vancouver, Canada. Article published: Dhalla et al. (2007). AIDS Care, 19, 1118-1127. Reprinted by permission of Taylor & Francis, Ltd. Email: shayestadhalla@yahoo.com
Slide 2 : Overview Both preventive (HIV-negative) and therapeutic (HIV-positive) HIV vaccine trials have been conducted. No Phase 3 HIV vaccine trials have been successful. Vaccine preparedness studies (VPS) are an important precursor to assess trial feasiblity. Willingness to participate in an HIV vaccine trial and retention can be assessed by a VPS. Motivations and barriers can also be assessed.
Slide 3 : HIV Vaccine Trials For preventive trials, it is necessary to attract retainable high-risk candidates. If HIV seroconversion is too low, a Phase 3 trial would be uninformative because the sample size required would be too large to show an effect. Mortality rates, risk-reduction interventions such as counseling, and HAART treatment contribute to a lower HIV incidence.
Slide 4 : HIV Vaccine Preparedness Studies ? Of the 30 OECD countries, locations of VPS include the US, Canada, Australia, and Europe (UK, Italy). VPS have dated back to 1992. Populations included injection drug users (IDU), men who have sex with men (MSM) and women at heterosexual risk (WAHR).
Slide 5 : Reviewed Willingness to Participate Studies In general, there was high interest in HIV vaccine trial participation. Willingness to participate has decreased in the last few years in Australia (Van de Ven, 2002 & 2006), the UK (Sherr, 2004) and Italy (Starace, 2006). Willingness to participate ranged from 41-86% in IDU, 23-94% in MSM, and 81% in the one study involving WAHR.
Slide 6 : Willingness to Participate
Slide 7 : Willingness to Participate High-risk behaviors such as sharing needles, frequent injections and needle-exchange program attendance were associated with willingness to participate. Other high-risk associations included sex with an HIV-positive partner or casual partner, and unprotected anal intercourse.
Slide 8 : Reviewed Retention Studies Retention refers to completion of study visits in an HIV VPS for follow-up interviews, counseling, and HIV antibody testing. 12-month retention ranged from 67-98% in IDU, 84-89% in MSM, and 67-92% in WAHR. A 3% retention rate was found in one study of IDU in Connecticut: this may have been due to unstable housing or the study site moving 4 months into the study.
Slide 9 : Retention Rates
Slide 10 : Motivations and Barriers Altruism was the biggest motivator to participate. Barriers included fear of contracting HIV/AIDS from the vaccine, vaccine-induced seropositivity, fear of side effects, and disturbances in personal relationships.
Slide 11 : Merck HIV Vaccine Trial / Conclusion A major barrier to vaccine trial participation identified recently, is that vaccine exposure might increase the risk of HIV infection. This was found in a study of the Merck adenovirus (Ad5) HIV vaccine (STEP study). (Kresge, K.J. (2007), International AIDS Vaccine Initiative Report, 11). There were 49 (5.36%) of 914 male recipients compared to 33 (3.58%) of 922 male placebo recipients who developed HIV infections. There was an increasing ratio of HIV infections among vaccinees compared to placebo with increasing levels of Ad5 antibody levels. This study was terminated in 2007. Although willingness to participate and retention have generally been adequate to conduct HIV vaccine trials, the effect of the STEP study on willingness to participate in future vaccine trials needs to be evaluated. (Dr. Kenrad Nelson, Johns Hopkins University).

 


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