Solid lines show baseline parameterisation of rates of mutation reversion, effect of NRTI resistance on acquisition of a dolutegravir drug-resistance mutation, effect of dolutegravir resistance on its efficacy, transmission probability of dolutegravir drug-resistance mutations in an HIV-transmission event, and the proportion of people with detectable drug levels on failing dolutegravir-based antiretroviral therapy. Shaded areas show uncertainty intervals (appendix p 13). Dots and error bars correspond to population mean and uncertainty range, respectively. Dolutegravir rollout was started in 2020. Viral suppression (ie, viral load less than 1000 copies per mL) on dolutegravir-based antiretroviral therapy was high depending on model assumptions for dolutegravir resistance; we estimated that up to 6–8% of people on dolutegravir-based antiretroviral therapy could be virally unsuppressed. Acquired dolutegravir resistance was defined as the proportion of people with intermediate or high dolutegravir resistance on failing dolutegravir-based antiretroviral therapy. Transmitted dolutegravir resistance was defined as the proportion of newly diagnosed people with intermediate or high dolutegravir resistance among those newly diagnosed with HIV. NNRTI=non-nucleoside reverse transcriptase inhibitor. NRTI=nucleoside reverse transcriptase inhibitor.