Comparison of phylogenetic divergence, transmission fitness and viral load between placebo and TFV arms. A, Comparison of phylogenetic divergence from the consensus subtype C reference sequence from the same geographic region. The phylogenetic distance median for TFV = 0.048 (IQR 0.043–0.054) and for placebo = 0.055 (IQR 0.049–0.061). B, Transmission index comparison between gag sequences from the TFV [median = 0.011 (IQR −0.006 to 0.024)] and those from the placebo [median = −0.004 (IQR −0.021 to 0.006)] recipients. C, Correlation between the baseline viral load and transmission index. D, Comparison of plasma viral loads at 12 months post infection between participants from the TFV [median viral load = 4.46 (IQR 4.06–4.78)] and placebo groups [median viral load = 3.83 (IQR 3.30–4.65)] (one participant from the placebo group did not have viral load data at or close to 12 months post infection).