Objective: We investigated whether previous treatment interruptions are associated with a raised risk of viral rebound in individuals who have attained virological suppression.
Methods: All patients achieving an undetectable viral load while on therapy were followed until viral rebound or the time of the last viral load. Poisson regression was used to describe the independent impact of treatment interruptions on rebound rates.
Results: A total of 12,977 patients from the United Kingdom Collaborative HIV Cohort (UK CHIC) Study achieved a viral load of less than 50 copies/ml. These patients contributed a total of 37,314 person-years of follow-up. The overall rebound rate was 8.07 (7.78, 8.36) per 100 person-years. In adjusted analyses, rates of viral rebound were up to 64% higher (rate ratio 1.64; 1.43, 1.88) in those who had previously interrupted therapy compared with those who had not. Patients who had interrupted at detectable viral loads had up to a 74% (1.74; 1.42, 2.14) higher chance of rebounding compared with those who had not interrupted with a detectable viral load. We found no evidence to suggest interrupting treatment at an undetectable viral load was associated with viral rebound.
Conclusion: Among patients with an undetectable viral load, having previously interrupted therapy while the viral load was detectable is associated with a raised risk of rebound.