Immunogenicity and safety of a third dose of anti-SARS-CoV-2 BNT16b2 vaccine in liver transplant recipients.

Abstract

Background & AimsA strategy to improve the low rate of anti‐SARS‐CoV‐2 mRNA vaccine‐induced immunogenicity in liver transplant recipients (LTs) is urgently needed.MethodsWe analyzed the rate of positive (≥0.8 U/ml) anti‐SARS‐CoV‐2 receptor domain binding protein (RBD) antibody response two months after a third dose of the BNT16b2 vaccine in 107 LTs who completed the second vaccine dose seven months earlier.ResultsA positive anti‐SARS‐CoV‐2‐s‐RBD antibody response after the third vaccine dose was detected in 98 (91.6%) LTs compared to 82 (76.6%) after the second vaccine dose (p=0.003). The median of anti‐SARS‐CoV‐2 RBD antibody titers increased from 22.9 U/ml six months after the second to 3500 U/ml two months after the third vaccine dose (p<0.001). Fourteen (14.3%) responder patients presented antibody titers <100 U/ml, 57 (58.2%) between 100 and 9999 U/ml and 27 (27.6%) ≥10000 U/ml. Seropositivity after the second dose was maintained after the third dose. Independent predictors of antibody response failure after the third vaccine dose were taking a higher daily dose of mycophenolate mofetil (MMF, p<0.001) and had a lower (<60 ml/min/1.73m2) estimated glomerular filtration rate (p=0.007). Nine (9.1%) LTs experienced symptomatic SARS‐CoV‐2 infection after the third vaccine dose. Median antibody titers were not statistically different between infected and not infected LTs (1325 vs 3515 U/ml, p=0.678).ConclusionsThe third dose of the BNT16b2 vaccine increased the number of LTs who developed a positive anti‐SARS‐CoV‐2 s‐RBD antibody response. A proportion of patients remained unresponsive, mainly for modifiable factors, such the use of MMF or multiple immunosuppressants.