Design: Systematic review and meta-analysis of 59 observational studies
Population: People with HIV on ART with viral suppression, including 19,511 with immunological non-response
Primary outcome: Predictors of inadequate CD4 recovery
Effect: Advanced stage OR 2.66 (2.34–3.02); HCV OR 1.85 (1.50–2.28); TB OR 1.77 (1.41–2.21)

Some people with HIV reach an undetectable viral load on antiretroviral therapy but their CD4 count does not recover — immunological non-response. This meta-analysis of 59 studies, including 19,511 people with non-response, looked for the factors that predict it.

The strongest clinical predictor was advanced HIV stage at diagnosis (OR 2.66, 2.34–3.02), along with low baseline and nadir CD4 counts. Hepatitis C coinfection (OR 1.85), tuberculosis (OR 1.77), injecting drug use (OR 1.67), hepatitis B (OR 1.30), male sex (OR 1.33) and older age were also linked. The review listed 57 candidate biomarkers, none ready for clinical use.

The message is mostly about timing: the later treatment starts, the less completely immunity returns. For those already affected, it identifies who needs closer watching for opportunistic infection and who should stay on prophylaxis longer, even with a suppressed viral load.

Expect slower CD4 recovery in people diagnosed late or with a very low nadir CD4.
Screen for hepatitis B, hepatitis C and tuberculosis, each linked to poor recovery.
Base decisions on stopping co-trimoxazole or other prophylaxis on the CD4 count, not on viral suppression alone.
Early diagnosis and treatment remain the main way to prevent non-response.

Why it matters

An undetectable viral load does not mean the immune system has recovered, especially after a late diagnosis.

The statistics, in plain English

These are pooled odds ratios from mainly observational studies. An OR of 2.66 for advanced stage means more than double the odds of non-response, but the studies differed in how they defined non-response, which limits precision.