ABSTRACT
Background. Accessible SARS-CoV-2-specific immunoassays may inform clinical management in people with HIV, particularly in case of persisting immunodysfunction. We prospectively studied their application in vaccine recipients with HIV, purposely including participants with a history of advanced HIV infection. Methods. Participants received one (n=250), two (n=249) or three (n=42) doses of the BNT162b2 vaccine. Adverse events were documented through questionnaires. Sample collection occurred pre-vaccination and a median of 4 weeks post-second dose and 14 weeks post-third dose. Anti-spike and anti-nucleocapsid antibodies were measured with the Roche Elecsys chemiluminescence immunoassays. Neutralising activity was evaluated using the GenScript cPAss surrogate virus neutralisation test, following validation against a Plaque Reduction Neutralization Test. T-cell reactivity was assessed with the Roche SARS-CoV-2 IFNγ release assay. Results. Primary vaccination (2 doses) was well tolerated and elicited measurable anti-spike antibodies in 202/206 (98.0%) participants. Anti-spike titres varied widely, influenced by previous SARS-CoV-2 exposure, ethnicity, intravenous drug use, CD4 counts and HIV viremia as independent predictors. A third vaccine dose significantly boosted anti-spike and neutralising responses, reducing variability. Anti-spike titres >15 U/mL correlated with neutralising activity in 136/144 paired samples (94.4%). Three participants with detectable anti-S antibodies did not develop neutralising responses post-third dose, yet displayed SARS-CoV-2 specific IFNγ responses. Conclusions: SARS-CoV-2 vaccination is well-tolerated and immunogenic in adults with HIV, with responses improving post-third dose. Anti-spike antibodies serve as a reliable indicator of neutralising activity. Discordances between anti-spike and neutralising responses may be accompanied by detectable IFN-γ responses, underlining the complexity of the immune response in this population.