Anti-RBD IgG4 Antibodies Surge After Third mRNA Jab

A group of biomedical researchers based out of Fukuoka University in the southern Japanese prefecture investigate what they describe as the longitudinal kinetics of RBD-specific IgG subclass antibodies in sera of Japanese healthcare workers received not only the second and third, but also their fourth doses of mRNA-based COVID-19 vaccines. Michinobu Yoshimura in the Department of Microbiology & Immunology, Faculty of Medicine, Fukuoka University and colleagues report that the anti-RBD IgG subclass in sera of patients with COVID-19-infected who had not received the COVID-19 vaccine were also examined. The physicians and scientists then compared anti-RBD IgG subclass antibody titers in the serum of pre-breakthrough-infected vaccinees and non-infected vaccinees. This study was set up given the investigators' presumption as to the importance of analyzing any consequence of repeated exposure to mRNA vaccines on SARS-CoV-2-spike receptor binding domain (RBD)-specific immunoglobulin (Ig)G subclass as well as the possible causal relationship with breakthrough infection. Yoshimura and colleagues report that “repeated vaccinations induce delayed but drastic increases in anti-RBD IgG4 responses.” But what does this mean? The Japanese team points to the need for additional investigation to better understand, or even reveal the magnitude of the high contribution of spike-specific IgG4 subclasses after repeated mRNA-based COVID-19 vaccination.”

This study was published in the International Journal of Infectious Diseases thanks to grants via the Japan Society for the Promotion of Science, the Japanese authors express gratitude to the staff at the university as well as thanks for reagents obtained from various partner organizations including BEI Resources and the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health.