Korean J Transplant.  2022 Nov;36(Supple 1):S10. 10.4285/ATW2022.F-0851.

Humoral immunogenicity of two doses of BNT162b2 in pediatric solid organ transplant recipients

• Baek JY
• Ihn K
• Koh H
• Lee KH
• Kim MY
• Kim S
• Kang JM
• Choi JY
• Park Y
• Kim MS

• KMID: 2535126
• DOI: http://doi.org/10.4285/ATW2022.F-0851

Abstract

Background
Pediatric solid organ transplant recipients (SOTRs) are at high risk of severe COVID-19, but studies on their COVID-19 vaccine immunogenicity are lacking. We investigated the humoral immunogenicity of pediatric SOTRs after two doses of BNT162b2 (BNT).
Methods
This prospective study was conducted at Severance Hospital in Seoul from October 2021 to March 2022. Pediatric SOTRs who received BNT/BNT were included as participants. Serum samples were collected between 14 days and 150 days after vaccination. We evaluated SARS-CoV-2 anti-S IgG titers, surrogate neutralization inhibition and plaque reduction neutral-ization test (PRNT) against wild-type (WT), Delta and Omicron. For comparison, serum samples from adult SOTRs (n=15) and healthcare workers (HCWs, n=12) vaccinated with BNT/BNT were used.
Results
Twelve pediatric SOTRs were included. The median age at SOT was 10 years (7–12 years), and the male to female ratio was 1:1. The median time from SOT to vaccination was 49 months (33–98 months), and 50% of them were taking two or more immunosuppressants. Pediatric SOTRs (92%) showed significantly higher anti-S IgG positivity than adult SOTRs (67%, P=0.002) and similar positivity to HCWs (100%, P>0.59). In the neutralization assay, the median inhibition of WT in pediatric SOTR was 98%, Delta was 97%, and Omicron was 12%, which was significantly lower for Omicron than the others (P<0.001). The PRNT results were similar to those of the surrogate neutralization assay, except that the ND50 titer of Delta (147.5) was significantly lower than that of WT (409.0, P=0.03).
Conclusions
After BNT/BNT, the humoral responses in the pediatric SOTRs were not lower than those in the adult SOTRs. How-ever, the immunogenicity against Omicron variant was very poor. Since humoral immunogenicity results may be different be-tween strains and test methods, caution is required when interpreting the humoral responses in these SOTRs.