Serological Response to the BNT162b2 COVID-19 mRNA Vaccine in Adolescent and Young Adult Kidney Transplant Recipients.

Haskin, Orly; Ashkenazi-Hoffnung, Liat; Ziv, Noa; Borovitz, Yael; Dagan, Amit; Levi, Shelly; Koren, Gili; Hamdani, Gilad; Levi-Erez, Daniella; Landau, Daniel; Alfandary, Hadas

BACKGROUND Initial reports in adult kidney transplant recipients (KTR) indicate low immunogenicity after 2 doses of the BNT162b2 COVID-19 mRNA vaccine. We describe the immunogenicity of this vaccine compared to the serologic response in naturally infected COVID-19 positive adolescent and young adult KTR. METHODS For this prospective observational study, the study group included 38 KTR who received 2 doses of the tested vaccine; the control group included 14 KTR who had a previous PCR-confirmed COVID-19 infection. RESULTS The mean age was 18±3 years. Positive serologic responses were observed in 63% and 100% of the study and control groups, respectively (p=0.01). Antibody titers were almost 30-fold higher in the control than the study group [median, interquartile range (IQR): 2782 (1908-11 000) vs. 100.3 (4.7-1744) U/mL, p<0.001), despite the longer time from the COVID-19 infection to serologic testing compared to time from vaccination [median (IQR): 157.5 (60-216) vs 37 (20.5-53) days, p=0.011]. Among vaccinated patients, higher proportions of those seronegative than seropositive were previously treated with rituximab (50% vs. 8%, p=0.01). Time from the second vaccine dose to serologic testing was longer in seropositive than seronegative patients [median, (IQR) 24.5 (15, 40) vs. 46 (27, 56) days, p=0.05]. No patient developed symptomatic COVID-19 disease postvaccination. CONCLUSIONS The BNT162b2 COVID-19 mRNA vaccine yielded higher positive antibody response in adolescent and young adult KTR than previously reported for adult KTR. Antibody titers after vaccination were significantly lower than following COVID-19 infection. Longer time may be required to mount appropriate humoral immunity to vaccination in KTR.