ABSTRACT

Objective

This study aims to compare and describe three local cases of allogeneic hematopoietic stem cell transplant recipients who developed graft-versus-host disease (GVHD) shortly after receiving COVID-19 mRNA vaccines.

Cases

Here we report three local, in-hospital cases of hematopoietic stem cell transplant patients who developed symptoms of GVHD after administration of the COVID-19 mRNA vaccine. Two patients had their vaccination 5-6 months after transplant, while 1 patient received it 1.2 years later. General symptoms included generalized rashes, oral sores, and loose stools. All developed symptoms 5-7 days after the first dose, with the majority occurring after the first dose. All three patients' symptoms resolved with steroid administration, and none required admission to the intensive care unit.

Discussion

Graft-versus-host disease after mRNA vaccines is one of the most serious but underreported complications of vaccination among stem cell transplant recipients. The pathophysiology behind this phenomenon is yet to be fully understood. A proposed mechanism is vaccine-induced autoimmunity through molecular mimicry, wherein certain pathogenic elements contained in the vaccine share significant similarity with specific human proteins. These proteins may serve as pathogen-associated molecular patterns (PAMPs), potentially explaining why not all post-HSCT patients develop GVHD.

Summary

While none of the patients developed severe adverse reactions, GVHD should be carefully monitored among post-allogeneic hematopoietic stem cell transplant recipients who received COVID-19 vaccination. Guidelines still recommend COVID-19 vaccination for these patients due to their high risk of developing severe COVID infections. However, closer monitoring and follow-up must be conducted, especially during the first 5-7 days after administration.