In addition, four plasma samples from episodes of breakthrough DNAemia occurring due to antiviral drug resistance in patients receiving MBV (two samples from a kidney transplant recipient -KTR- and one from a HSCTR) or LTV (one HSCTR) were tested for UL21.5 mRNA, as well as samples from 5 patients (one KTR and four HSCTR) developing self-resolving transient DNAemia “blips” (not associated with antiviral drug resistance) during LTV prophylaxis.