Table 1.

HIV vaccine efficacy trials.

Efficacy trial	Vaccine	Population	N	Efficacy	Other significant results	Immune response	Immune correlates of risk
VAX004	AIDSVAX B/B (rgp120 immunogens)	Primarily high-risk MSM	5403	None [Flynn et al. 2005]	N/A	Weak nAb response [Gilbert et al. 2010]	N/A
VAX003	AIDSVAX B/E (rgp120 immunogens)	Injection drug users	2546	None [Pitisuttithum et al. 2006]	N/A	Weak nAb response [Montefiori et al. 2012]	N/A
Step	MRKAd5 HIV-1 (rAd5 vector expressing Gag, Pol, and Nef)	Primarily high-risk MSM	3000	None; trial halted after meeting prespecified futility boundaries [Buchbinder et al. 2008]	Significantly increased risk of HIV infection in men who were both Ad5-seropositive and uncircumcised, which waned with time since vaccination [Duerr et al. 2012]	CD8+ T-cell response detected in the majority of vaccinees, although weak and of narrow breadth [McElrath et al. 2008]	N/A
HVTN 503/Phambili	Same as Step	Primarily heterosexuals	801	None; enrollment halted after lack of efficacy seen in Step [Gray et al. 2011b]	N/A	Similar to Step [Gray et al. 2011b]	N/A
RV144	ALVAC (canarypox vector expressing Env, Gag, and Pol) prime followed by AIDSVAX B/E boost	Primarily low-risk heterosexuals	16,402	31.2% overall efficacy for prevention of HIV-1 infection in the modified intention-to-treat analysis [Rerks-Ngarm et al. 2009]; no subsequent effect on viremia or CD4 count in vaccinees who were infected [Rerks-Ngarm et al. 2012]	68% efficacy for low or medium risk participants, no efficacy in the high-risk group; efficacy was highest over the first 12 months and then fell rapidly [Robb et al. 2012]	Weak nAb response [Montefiori et al. 2012]. Moderate CD8+ and CD4+ T- cell response; the CD4+ T-cell response was directed against the V2 region of Env [de Souza et al. 2012]	Binding of IgG to the V1 and V2 regions of Env correlated with protection; protection was mitigated by the presence of plasma IgA directed against Env [Haynes et al. 2012a]
HVTN 505	VRC-HIVDNA016-00-VP (DNA expressing Gag, Pol, Nef, and Env) prime followed by VRC-HIVADV014-00-VP (rAd5 expressing Gag, Pol, and Env) boost	High-risk MSM	2504	None; trial halted after meeting prespecified futility boundaries	Awaiting final trial results	Awaiting final trial results	N/A

HIV, human immunodeficiency virus; HVTN, HIV Vaccine Trials Network; IgG, immunoglobulin G; MSM, men who have sex with men; nAb, neutralizing antibody; rgp, recombinant glycoprotein; rAd5, recombinant adenovirus serotype 5.