In the genetic models, we analyzed the heterogeneity of 5/5 vs. the other genotypes by using the healthy subjects as controls. The results indicated a low heterogeneity (X 2 = 9.30, I 2 = 25%, p = 0.23) ( Figure 3A ). Next, we pooled the 8 studies under the fixed effect model. The pooled OR was 0.90 (95% CI = 0.71-1.44, p = 0.38) ( Figure 3A) . Then, we analyzed the heterogeneity of 5/5 vs. the other genotypes by using the HIV-1 exposed but seronegative samples subjects (HESN) as controls ( Figure 3B) . The results indicated a low to moderate heterogeneity (X 2 = 7.09, I 2 = 29%, p = 0.21). The fixed effect model was then used to synthesize the data. Overall, the pooled OR was significant at 0.68 (95% CI = 0.50-0.93, p = 0.01) ( Figure 3B ). These results suggested that the 5/5 homozygous genotype showed a significantly reduced risk of HIV-1 infection in HIV-1 exposed seronegative individuals (HESN) but not in healthy individuals. A summary of the results of all the comparisons with different genetic models was listed in Table S1 .