Table 1 displays characteristics of the three cohorts. In comparison with individuals from the two African settings, the population from the SHCS is dominated by older male individuals. The median HIV-1 copies/mL plasma RNA values at treatment failure were the highest in Uganda (24 613.5) and the lowest in the SHCS (10 244), whereas the median CD4+ T cells/mm³ were the lowest in Uganda (257.5) and the highest in the SHCS (431). In terms of regimens at treatment failure, there was a similar distribution of NNRTIs, but more variability in terms of NRTIs. Notably, in Uganda 15.0% of individual genotyping did not reveal low-level resistance (or higher) to any drug of their ART regimen at virological failure, whereas in Switzerland this was the case for 31.2% and in Lesotho for 6.9% of the individuals. In Uganda 15.0%, in Lesotho 39.7% and in the SHCS 3.3% of the individuals had high-level resistance to all three drugs of their first-line regimen. A high number of individuals (72.5% in Uganda, 81.0% in Lesotho and 50.8% in the SHCS) harboured HIV with high-level resistance to at least two drugs of their first-line regimen (Table 1), implying they were at most on one ‘fully active’ drug at the time of treatment failure. In our Supplementary data (available at JAC Online), this analysis was repeated only considering resistance to NRTIs, as they are the most essential for future treatment limitations in these patients.