Is it bad, is it good, or is IgG4 just misunderstood?

Repeated doses of mRNA vaccines for COVID-19 result in increased proportions of anti-Spike antibodies of the IgG4 subclass, that are known to neutralize well and to form mixed immune complexes with IgG1 but in a pure form might be less effective than IgG1 or IgG3 antibodies in facilitating opsonization by phagocytes, complement fixation, and NK cell-dependent elimination of infected cells (see related Research Article by Irrgang et al .).