AEGiS-15IAC: Preliminary results of a phase III HIV vaccine efficacy trial among injecting drug users in Thailand.

15th International AIDS Conference

Bangkok, Thailand - July 11-16, 2004

Preliminary results of a phase III HIV vaccine efficacy trial among injecting drug users in Thailand.

Int Conf AIDS 2004 Jul 11-16; 15:(abstract no. ThOrA1427)

Choopanya K, Tappero JW, Pitisuttithum P, Suntharasamai P, Kaewkungwal J, Vanichseni S, Martin M, Hu D, Sangkum U, Vimutisunthorn E, Natrujirote P, Heyward W, van Griensven F, Kitayaporn D
Bangkok Vaccine Evaluation Group, Bangkok, Thailand

BACKGROUND: The world's first phase III HIV vaccine trial in Asia was successfully completed in June 2003 in Thailand.

METHODS: The HIV vaccine trial started in March 1999. The trial was a collaborative effort involving the Bangkok Metropolitan Administration, the Thailand Ministry of Public Health (MOPH), Mahidol University, the U. S. Centers for Disease Control and Prevention (CDC), the Thai MOPH - U. S. CDC Collaboration, and VaxGen Inc. HIV-seronegative IDUs were randomized (1:1) to receive 7 doses of AIDSVAX B/E or placebo in a blinded fashion over 30 months. AIDSVAX B/E is a bivalent rgp120 vaccine developed to protect against HIV-1 subtypes B and E. Participants were followed for 36 months.

RESULTS: From March 1999 through August 2000, 4,943 IDUs were screened for enrollment; 1,689 were HIV-seropositive, 708 were excluded for other reasons, and 2,546 were enrolled. Immunization compliance was high (>97%) and volunteer follow-up was excellent (>95%). No vaccine-related serious adverse events were reported. Among enrolled participants, 229 became HIV-infected based on serologic testing; 18 of these were HIV-infected at enrollment by nucleic acid testing. Among the 211 who became HIV-infected during trial follow-up, 105 received placebo and 106 vaccine. HIV-1 subtype E was identified in 164 (77.7%) infected participants and subtype B in 47 (22.3%). The point estimate of vaccine efficacy was 0.1% (95% confidence interval, -30.8%, 23.8%). The HIV incidence rate was 3.1% per year. Reported frequency of drug injection and needle sharing declined significantly during the trial. Conclusion AIDSVAX B/E does not protect IDUs from HIV infection. The annualized HIV incidence was 3.1%. Drug injection and needle sharing declined, suggesting effective risk reduction counseling. With appropriate infrastructure, preparation, and training, scientifically sound and ethical phase III HIV vaccine trials can be completed among IDUs.

Keywords: AEGIS, AIDS Vaccines, Clinical Trials, Phase III, HIV-1, Thailand, HIV Infections, Needle Sharing, Acquired Immunodeficiency Syndrome, HIV Seropositivity, Incidence, Double-Blind Method, Counseling, Asia, AIDSVAX

040711
ThOrA1427