Long-term immune response after SARS-CoV2 vaccination in solid organ transplant recipients

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.

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.

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.

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.