Randomized, Double‐Blind, Placebo‐Controlled Efficacy Trial of a Bivalent Recombinant Glycoprotein 120 HIV‐1 Vaccine among Injection Drug Users in Bangkok, Thailand
1Department of Clinical Tropical Medicine, Mahidol University, and 2Bangkok Metropolitan Administration, Bangkok, and 3Thailand Ministry of Public Health–US Centers for Disease Control and Prevention Collaboration, Nonthaburi, Thailand; 4Statistical Center for HIV/AIDS Research and Prevention, Fred Hutchinson Cancer Research Center, Seattle, Washington; 5VaxGen, Inc., Brisbane, California; 6US Centers for Disease Control and Prevention, Atlanta, Georgia
Background.
In Thailand, phase 1/2 trials of monovalent subtype B and bivalent subtype B/E (CRF01_AE) recombinant glycoprotein 120 human immunodeficiency virus type 1 (HIV‐1) vaccines were successfully conducted from 1995 to 1998, prompting the first HIV‐1 vaccine efficacy trial in Asia.
Methods.
This randomized, double‐blind, placebo‐controlled efficacy trial of AIDSVAX B/E (VaxGen), which included 36‐months of follow‐up, was conducted among injection drug users (IDUs) in Bangkok, Thailand. The primary end point was HIV‐1 infection; secondary end points included plasma HIV‐1 load, CD4 cell count, onset of acquired immunodeficiency syndrome–defining conditions, and initiation of antiretroviral therapy.
Results.
A total of 2546 IDUs were enrolled between March 1999 and August 2000; the median age was 26 years, and 93.4% were men. The overall HIV‐1 incidence was 3.4 infections/100 person‐years (95% confidence interval [CI], 3.0–3.9 infections/100 person‐years), and the cumulative incidence was 8.4%. There were no differences between the vaccine and placebo arms. HIV‐1 subtype E (83 vaccine and 81 placebo recipients) accounted for 77% of infections. Vaccine efficacy was estimated at 0.1% (95% CI, −30.8% to 23.8%;
, log‐rank test). No statistically significant effects of the vaccine on secondary end points were observed.
Conclusion.
Despite the successful completion of this efficacy trial, the vaccine did not prevent HIV‐1 infection or delay HIV‐1 disease progression.
Received 28 February 2006; accepted 28 July 2006; electronically published 3 November 2006.
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Potential conflicts of interest: none reported.
Financial support: VaxGen, Inc.
Clinical Trial registration number: 36424.
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Study group members are listed after the text.





