Abstract
BACKGROUND: Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) vaccination in solid organ transplant (SOT) recipients is associated with suboptimal antibody response (AbR) favouring breakthrough infection (BI). The role of cell-mediated immunity (CMI) remains uncertain. METHODS: Single-center prospective longitudinal cohort study of adult SOT recipients monitored for both AbR and CMI at 6 ± 2 months after booster dosage of SARS-CoV-2 vaccine. Primary end-point was BI diagnosis and CMI was the main risk factor. Relationship between CMI and BI was investigated by bivariate tests and multivariable logistic regression. RESULTS: CMI was performed in 139 patients. In 66 patients BI was documented before CMI, thus 73 (33 kidney, 24 liver, 14 lung, 2 heart) were analysed. The first 2 vaccine doses consisted of BNT162b2 and mRNA-1273 in 69.1% and 30.9% of cases, respectively. Whereas mRNA-1273 was used as for third dose in 91.2% of patients. At a median of 215 (IQR 181-252) days after booster dose, 40 (54.8%) patients displayed both AbR and CMI, 21 (28.8%) only AbR and 12 (16.4%) neither AbR or CMI; there were no patients showing negative AbR and positive CMI. Overall, 22 (30.1%) patients reported BI with no significant differences between those with positive vs. negative CMI (59.1% vs. 40.9%, p = 0.798), confirmed by multiple logistic regression after adjusting for age, type of vaccine and organs, high AbR and time from transplant. CONCLUSION: Our data suggest that in the solid organ transplant population of our cohort, cell-mediated immunity does not appear to be a strong predictor of BI.