Original articles / Online first

Seroconversion following a booster dose of COVID-19 vaccine in liver transplant recipients. A systematic review and meta-analysis

Aikaterini Gkoufa, Vasileios Lekakis, George Papatheodoridis, Evangelos Cholongitas
Published online: March 06, 2023


Introduction: Although it is well established that two doses of COVID-19 vaccines are associated with reduced immune responses in liver transplant recipients [LTRs], studies regarding their immunogenicity and tolerability after a booster dose are limited.

Objectives: We aimed to review the available literature data regarding antibody responses and safety of the third dose of COVID-19 vaccines in LTRs.

Methods: We searched PubMed for eligible studies. The primary outcome was to compare the rates of seroconversion after the second and third COVID-19 vaccine dose in LTRs. Meta-analysis was performed using a generalized linear mixed model (GLMM) and the Clopper and Pearson method was used to calculate the two-sided confidence intervals (CI).

Results:  Six prospective studies involving 596 LTRs met the inclusion criteria. The pooled rate of antibody response before the third dose was 71% (95%CI:56-83%; heterogeneity: I2=90%, p<0.001), while after the third dose was 94% (95%CI:91-96%; heterogeneity: I2=17%, p=0.31). There was no difference in antibody responses after the third dose in relation to the use, or not, of calcineurin inhibitors (p=0.44) or mammalian target of rapamycin inhibitors (p=0.33), while the pooled rate of antibody responses in those under mycophenolate mofetil (MMF) was 88% (95%CI:83-92%; heterogeneity: I2=0%, p=0.57), significantly lower (p<0.001), compared to those under MMF-free immunosuppression [pooled rate:97%, 95%CI:95-98%; heterogeneity: I2=30%, p=0.22]. No safety concerns of the booster dose were reported.

Conclusions: Our meta-analysis demonstrated that the third dose of COVID-19 vaccines induced adequate humoral and cellular immune responses in LTRs, while MMF remained a negative predictor of immunological responses.

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