Figure 5.

Investigation of TTV viral load as potential predictive biomarker of response to a third vaccine dose in COVID-19-naive lung transplant recipients determined as nonresponders to the second dose. (A) TTV viral load measured after the second vaccine dose in nonresponders (n = 35) and responders (n = 12) to the third vaccine dose, with medians represented as solid horizontal lines. The dotted lines indicate the predictive thresholds of 6.2 log₁₀ cp/mL and 3.2 log₁₀ cp/mL associated with low and high rates of vaccine response, respectively. Comparison was computed with Mann-Whitney test using Graphpad Prism version 9.3.1. software. (B) Receiver operating characteristics (ROC) curve for prediction of vaccine response to the third dose based on TTV viral load measured in seronegative LTR after the second vaccine dose. Area under the curve (AUC): 0.9190. The upper threshold of 6.2 log copies/mL is associated with a negative predictive value of 100% (in case of high TTV viral load) and a positive predictive value of 40.0% (in case of low TTV viral load) for vaccine response. Conversely, the lower threshold of 3.2 log copies/mL is associated with a negative predictive value of 91.9% (in case of high TTV viral load) and a positive predictive value of 90.0% (in case of low TTV viral load) for vaccine response in this cohort. TTV: Torque teno virus. ****p value <0.0001.