Humoral and cellular responses to SARS-CoV-2 variants after ancestral COVID-19 vaccines in people with HIV and lung transplant recipients.

Objectives: Immunocompromised hosts have reduced immune responses to COVID-19 vaccination, and more severe disease. Antibody responses correlate with protection but markers of immunity vary across a spectrum of immunocompromise. We compared serologic and cellular responses following Ancestral COVID-19 vaccines in healthy controls (HC), people with HIV (PWH) and lung transplant (LTx) recipients. Methods: Anti-spike receptor binding domain (RBD) IgG, neutralising antibodies (nAb) and T-cell responses were assessed one-month post-dose 2 and dose 3 of Ancestral COVID-19 vaccination in HC, PWH and LTx. NAb responses to Ancestral, Delta and Omicron BA.2 and BA.5 variants were assessed. Results: Twenty-nine HC, 21 PWH and 12 LTx recipients were included. PWH demonstrated lower anti-RBD-IgG responses (median post-dose 3: 80.3 μg mL Conclusion: Although Dose 3 was beneficial, LTx recipients demonstrated lower serological responses than HC, while reductions were modest in PWH. Immunocompromised groups had reduced but detectable SARS-CoV-2-specific T-cell responses, demonstrating the utility of COVID-19 vaccination despite poorer serological responses.