RT Journal Article SR Electronic T1 Failure of on-demand pre-exposure prophylaxis: the risk of HIV drug resistance JF Sexually Transmitted Infections JO Sex Transm Infect FD BMJ Publishing Group Ltd SP 234 OP 234 DO 10.1136/sextrans-2021-055354 VO 98 IS 3 A1 Angelo Roberto Raccagni A1 Elena Bruzzesi A1 Nicola Gianotti A1 Michela Sampaolo A1 Diana Canetti A1 Antonella Castagna A1 Silvia Nozza YR 2022 UL http://sti.bmj.com/content/98/3/234.abstract AB