Clinical assessment before starting PrEP
Overall, the risk of developing TD* or FTC resistance among participants on PrEP is low (9). According to a World Health Organization (WHO) meta-analysis of HIV resistance data from randomised clinical trials of PrEP, participants on PrEP versus placebo who started PrEP at the time of acute HIV infection had a higher risk of developing resistance, with more cases of resistance developing to FTC than to TD*. Only a few TD* or FTC mutations were recorded among participants who seroconverted after randomisation into clinical trials (9). Similar findings were reported in a more recent review of clinical trials and case reports of HIV resistance occurring in the PrEP setting (10). Mathematical modelling shows that the number of HIV-1 infections that would be averted by PrEP greatly exceeds the number of drug-resistant infections that could occur (11).