Background: There are scarce data on poor immune response (PIR) despite viral suppression (VS) on ART in children. We assessed PIR prevalence, associated factors and clinical outcomes in EPPICC.
Methods: Children aged< 18-years at ART start, with ≥1 year follow-up, ≥1 viral load (VL) and CD4 measurements were eligible. VS was defined as VL≤400 copies/mL within 12-months of ART initiation
(< 18-months for infants) and sustained VL≤400 c/mL for ≥1 year (allowing unconfirmed rebound < 10,000 c/mL). PIR was defined as WHO ''advanced'' or ''severe'' immunological stage (CD4%< 30 for age< 12-months, CD4%< 25 for 12-35 months, CD4%< 20 for 35-59 months; CD4%< 15 or CD4< 350 cells/mm3 for ≥5-years). Follow-up was censored at confirmed VL>400c/mL, unconfirmed VL≥10,000c/mL or VL measurements gap of ≥15-months. Factors associated with PIR were explored using logistic regression. Rates of clinical events (death/CDC C) during VS were calculated by time-updated WHO immunological stage.
Results: Of 3,510 children starting ART, 2210(63%) had VS for ≥1 year: 47% male, 92% perinatally-infected. At ART initiation, median[IQR] age was 6.3yrs[2.1,10.4], CD4% 16% [8,24], 15% and 55% were WHO advanced and severe immunological stage, respectively. PIR was observed in 13%(248/1863), 7%(102/1437) and 4%(50/1155) of patients at 1-, 2- and 3-years of sustained VS. PIR was strongly associated with older age and worse immunological stage at ART start (Table). Among patients with VS for ≥1-year, there were 4 deaths and 50 CDC C events (2 and 15 among PIRs, respectively). The rate of clinical events was 1.94(95%CI 1.20, 3.12) per 100 person-years among PIRs versus 0.39(0.27,0.56) among responders (WHO immunogical stage “none”), p< 0.0001.
Conclusions: PIR despite VS was relatively rare in children but was associated with significantly increased risk of AIDS/death as compared to immune-responders. Predictors of PIR include older age and lower CD4 at ART start, supporting recommendations for immediate ART in all children.

Table. Factors associated with poor immune response in children with viral suppression >=1 year
[Table. Factors associated with poor immune response in children with viral suppression >=1 year]