Sourced of - Vejon Health - https://www.youtube.com/watch?v=fpAKi2poiWw The concern is regarding recurrent mild breakthrough COVID-19 infections across highly vaccinated regions. Could they indicate longer term risks? Kiszel, Petra, et al. "Class switch towards spike protein-specific IgG4 antibodies after SARS-CoV-2 mRNA vaccination depends on prior infection history." Scientific Reports 13.1 (2023): 13166. https://www.nature.com/articles/s41598-023-40103-x#Abs1 Nagata, Keiko, et al. "Epstein–Barr virus lytic reactivation induces IgG4 production by host B lymphocytes in Graves' disease patients and controls: a subset of Graves' disease is an IgG4-related disease-like condition." Viral immunology 31.8 (2018): 540-547. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6205085/