Effects of FcγRIIIa genotypes, vaccine status, and behavioral risk scores on HIV infection rates. Vaccinees with the FcγRIIIa VV genotype have similar infection rates whether in the high behavioral risk or low behavioral risk groups (A). However, behavioral risk is a strong predictor of infection rates for vaccinees with the FV (C) or FF (E) genotypes and for placebo recipients with the VV (B), FV (D), or FF (F) genotypes. Hazard ratios and P values are shown for the comparison between low risk and high risk; the small number of VV placebo recipients results in an unstable hazard ratio and incalculable P value.