Study design and population
We performed a retrospective cohort study among PWH under routine follow-up at the Infectious Diseases Unit of the IRCCS Ospedale Maggiore Policlinico in Milan, Italy and enrolled in the Polimmune study, an analysis conducted in our centre about immunogenicity of COVID-19 vaccines. Inclusion criteria were age >18 years, immunization with mRNA-1273 vaccine according to the schedule of attendance in the context of the Italian national vaccination program (a primary schedule of 2 doses given 28 days apart followed by 1 booster dose around 10 months after the first shot) and being stable on ART for 18 months before vaccination achieving viral suppression, defined as VL <200 copies/mL. The main outcome was the occurrence of a VB, defined as a VL between 20-200 copies/mL, in the 12 months since the first vaccination shot. As a comparison, we evaluated the occurrence of VB among the same individual in the 12 months before vaccination.
Demographic and clinical data were extracted from electronic medical records. Participants had outpatient clinic visits every 4 months in agreement with the Italian guidelines, performing VL quantification and immunologic profiling at each time. Good adherence to ART was defined as taking >90% of the doses according to the patient self-report. Optimal immunologic response (OIR) was defined as CD4+ T/CD8+ T ratio ≥1 plus CD4+ T ≥500cells/µL plus CD4+ T ≥30%. Virologic failure was defined as the detection of HIV RNA >200 copies/mL in at least two separate blood samples. As part of the Polimmune study, enrolled individuals provided blood samples at T0 (enrolment), T1a (one month after the first dose), T1b (one month after the second dose), T3 (three months after the first dose), T6 (six months after the first dose), and T1c (one month after the first booster dose). SARS-CoV-2 anti-N antibodies were assessed at T0, T3, T6 and T1c whereas anti-S antibodies and antibody neutralisation activity (ND50) were assessed at T1b.