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Pseudo-Anaphylactic Reactions to Pfizer BNT162b2 Vaccine: Report of 3 Cases of Anaphylaxis Post Pfizer BNT162b2 Vaccination

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posted on 01.12.2021, 06:25 by Xin Rong Lim, Pui Lam Bernard LeungPui Lam Bernard Leung, Carol Yee Leng Ng, Justina Wei Lynn Tan, Grace Yin Lai Chan, Chien Mei Loh, Gwendolyn Li Xuan Tan, Valerie Hui Hian Goh, Lok To Wong, Chong Rui Chua, Sze Chin Tan, Samuel Shang Ming Lee, Hwee Siew Howe, Bernard Yu Hor Thong, Khai Pang Leong
Anaphylactic reactions were observed after Singapore's national coronavirus disease 2019 (COVID-19) vaccination programme started in December 2020. We report the clinical and laboratory features of three patients in our institution who developed anaphylactic reactions after receiving the Pifzer BNT162b2 vaccine. IgM and IgG antibodies, but not IgE antibodies to the Pfizer BNT162b2 vaccine, were detected in all subjects. Similarly, mild to high elevated levels of anti-polyethylene glycol (PEG) IgG (1035-19709 U/mL, vs. vaccine-naive < 265 U/mL, vaccine-tolerant < 785 U/mL) and IgM (1682-5310 U/mL, vs. vaccine-naive < 1011 U/mL, vaccine-tolerant < 1007 U/mL) were detected in two out of three patients via commercial ELISA. High levels of serum anaphylatoxin C3a (79.0 +/- 6.3 mug/mL, mean +/- SD, vs. normal < 10 mug/mL) were observed in all three patients during the acute phase of the reaction, while tryptase levels, a marker of mast cell activation, were not elevated. Finally, one patient with the highest levels of anti-PEG IgG, IgM, and anti-Pfizer BNT162b2 IgG and IgM exhibited an enhanced Th2 cytokine serum profile during an acute reaction, with high levels of IL-4 (45.7 pg/mL, vs. vaccine-naive/tolerant < 2.30 pg/mL), IL-33 (86.4 pg/mL, vs. vaccine-naive/tolerant < 5.51 pg/mL) and IL-10 (22.9 pg/mL, vs. vaccine-naive/tolerant < 12.49 pg/mL) diminishing over time following corticosteroid treatment.


FY2021LXR/National Centre for Infectious Disease Catalyst Grant.


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This is the publisher's PDF version of: Lim, X.R.; Leung, B.P.L.; Ng, C.Y.L.; Tan, J.W.L.; Chan, G.Y.L.; Loh, C.M.; Tan, G.L.X.; Goh, V.H.H.; Wong, L.T.; Chua, C.R.; Tan, S.C.; Lee, S.S.M.; Howe, H.S.; Thong, B.Y.H.; Leong, K.P. Pseudo-Anaphylactic Reactions to Pfizer BNT162b2 Vaccine: Report of 3 Cases of Anaphylaxis Post Pfizer BNT162b2 Vaccination. Vaccines 2021, 9, 974. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( 4.0/).

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