"Abstract: Humoral immune responses after BNT162b2 vaccination are predominantly composed of immunoglobulin (Ig) G1 and IgG3 subclass antibodies. As previously described in adults, S1-specific and receptor-binding domain–specific IgG4 levels increase significantly 1 year after the second BNT162b2 vaccination in children 5-11 years of age...
In summary, we report on increased spike-specific IgG4 levels in children 1 year after BNT162b2 vaccination, such as the effect observed in adults. While our study does not allow to predict effects on population level due to the small cohort size, it gives insight into the longitudinal dynamics of the spike-specific IgG subclass composition in children. IgG4 responses should gain more attention in health and disease, especially in the context of mRNA vaccination. Understanding the unusual mechanism triggering IgG4 production is crucial, as more mRNA vaccines are currently under development and could hit the global market soon."