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HIV
CARE
Betty J. Dong, Section Advisor
HIV vaccine shows a modest benefit in reducing transmission
Key point: A community-based trial involving more
than 16,000 young Thai adult men and women showed that administration of
four priming injections with ALVAC-HIV and two booster injections of
AIDVAX B/E vaccine resulted in possibly modestly reduced transmission of
HIV-1 infection in low- to moderate-risk heterosexual subjects.
Finer points: Results from the Ministry of Public
Health–Thai AIDS Vaccine Evaluation Group (MOPH–TAVEG) trial
were released on October 20. MOPH–TAVEG randomized 16,402 young
adults from two provinces in Thailand to six HIV-1 vaccinations (n =
8,202) or placebo vaccinations (n = 8,200). Subjects who received the
active vaccinations were given 4 priming injections with ALVAC-HIV at
weeks 0, 4 (range 3–7 weeks), 12 (range 10–15 weeks), and 24
(range 21–28 weeks), and two booster injections of AIDVAX B/E
vaccine at weeks 12 and 24. Subjects were evaluated at the end of the
6-month vaccination series and every 6 months thereafter for 3
years.
Baseline demographics were similar between the two groups; the
majority of subjects were male (61.4%), between 21 to 25 years of age
(45%), married (50%), and at low (47.5%) or moderate (28.4%) risk for
HIV-1 infection. Over 52,985 person-years of follow-up, 132 subjects
became infected with HIV-1—56 in the vaccine group and 76 in the
placebo group. The vaccine’s observed efficacy in preventing HIV-1
infection in the intention-to-treat (ITT) analysis (n = 16,402) was
26.4% (P = 0.08), 26.2% (P = 0.16) in the per-protocol analysis (n =
12,542), and 31.2% (P = 0.04) in the modified-ITT analysis (n = 16,395).
The modified-ITT analysis excluded 7 subjects with confirmed HIV-1
infection at baseline. The vaccine had no effect on HIV-1 viral load
reductions or CD4 T-cell counts in subjects who became infected. Most
adverse reactions were mild to moderate in severity, and approximately
69.4% of subjects in both groups reported at least one adverse
event.
What you need to know: This is the first and only
HIV-1 vaccine trial showing possible prevention of disease transmission.
An accompanying editorial pointed out that other failed HIV-1 vaccine
trials were conducted in primarily high-risk subjects, defined as men
who have sex with men and intravenous drug abusers, and that the current
trial was composed of low-risk and moderate-risk heterosexual subjects.
Dolin explained that "perhaps the requirements for protection against
transmission in low-risk, heterosexual persons are considerable
different or less stringent than those in high-risk subjects." The
MOPH–TAVEG investigators and other experts agree that the current
results are promising; however, further research is needed.
What your patients need to know: Counsel patients
that while the current trial is promising, solid conclusions cannot be
made without further research. This vaccine is targeted toward viral
strains found primarily in Thailand.
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