Phase
III Clinical Trials of gp-120 based AIDS vaccine in Thailand:
The following article has been reproduced with permission from the Center for
disease control, Atlanta. www.cdc.gov
Among
the 60 million inhabitants of Thailand, as many as 800,000 people are currently
believed to be living with HIV. Despite
innovative and persistent prevention efforts, HIV continues to spread rapidly,
particularly among Thailand’s population of injection drug users (IDUs).
Methadone treatment, education and counseling on HIV prevention, and easy access
to sterile needles have certainly helped to slow the epidemic. Yet, among IDUs
in Bangkok, 6% continue to become infected each year. In addition to being one
of the nations most severely affected by HIV, Thailand has emerged as one of the
nations most committed to ending its toll. To address the urgent need for an HIV
vaccine, Thai officials have been working with the World Health Organization,
the Joint United Nations Program on HIV/AIDS (UNAIDS), the International AIDS
Vaccine Initiative (IAVI), the Government of Japan, the U.S. National Institutes
of Health (NIH), the U.S. Department of Defense, various universities, and the
Centers for Disease Control and Prevention (CDC) since 1991 to prepare for HIV
vaccine efficacy trials. In February 1999, Thailand became the first developing
nation to announce a Phase III vaccine field trial. A Phase III trial is done to
determine if a vaccine is effective in protecting against infection or disease
and is an important step in the evaluation process leading to licensure.
AIDSVAX
Phase 3 Trial in Thailand :
As
part of the Thai National Plan for HIV vaccine research, the Bangkok
Metropolitan Administration (BMA) is leading the 3-year collaborative research
trial to evaluate the ability of AIDSVAX to prevent HIV infection among
uninfected IDUs in Bangkok, Thailand. AIDSVAX was developed by VaxGen, a U.S.
vaccine developer. BMA is conducting the trial in conjunction with VaxGen, the
Mahidol University Faculty of Tropical Medicine in Bangkok, and the HIV/AIDS
Collaboration (a longstanding research collaboration between the Thai Ministry
of Public Health and CDC). The trial is being conducted among uninfected IDUs
attending 17 drug treatment clinics in Bangkok. The design is a randomized,
double-blind, placebo-controlled trial in which half of the 2,500 volunteers
receive the AIDSVAX vaccine and the other half receive placebo injections that
do not include the vaccine. Neither the researchers nor the participants know
which participants are in each half of the trial.
To guard against the relaxation of preventive behaviors, all volunteers
receive extensive counseling on how to protect themselves against HIV infection,
as well as explicit warnings that this vaccine may not protect them from
infection. To further ensure that trial participants are not inadvertently
placed at any risk, the trial design, as well as all procedures and protocols
for study recruitment and counseling, have received extensive scientific and
ethics review by Institutional Review Boards and ethics committees of all
involved agencies, both the Thai and U.S. government, and the Joint United
Nations Program on HIV/AIDS.
Composition
of the AIDSVAX vaccine:
AIDSVAX
is a "bivalent" vaccine, meaning it is composed of gp120 proteins
found on the outer envelope of two strains of HIV. The version of the vaccine
being tested in Thailand is designed to induce antibodies to HIV-1 subtypes B
and E, the subtypes of HIV most common in South East Asia and the Pacific Rim.
VaxGen is currently evaluating another version of AIDSVAX designed to protect
against strains common in North America among 5,000 volunteers in multiple sites
throughout the United States. Thai health officials played a leading role in
acknowledging the critical need for a vaccine designed for use in Thailand to
protect against strains of both subtypes B and E. Early reports from several
smaller trials of AIDSVAX in Thailand and the United States, involving about
2,000 persons, have shown the vaccine to be safe and capable of inducing
antibodies against these strains of HIV.
Similar
Vaccine trials in the US:
Although AIDSVAX is the first vaccine to move to Phase lll trials in a
developing country, as well as in the United States, it is only one of a series
of vaccines that are in various stages of the development process. The National
Institutes of Health (NIH) is the agency responsible for coordinating the
simultaneous evaluation of multiple vaccine candidates in the United States.
