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

Abstract

Background & Aims

A strategy to improve the low rate of anti‐SARS‐CoV‐2 mRNA vaccine‐induced immunogenicity in liver transplant recipients (LTs) is urgently needed.

Methods

We 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.

Results

A 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).

Conclusions

The 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.