A second study looking at effects on antibodies including IgG4 post 4X Pfizer mRNA shots in comparison to two AstraZeneca followed by 3X mRNA shots. Unclear evidence might suggest that prior infection to vaccination might no longer protect against the IgG4 rise, as well as post non-mRNA shots. A mechanistic reason for why the rise of IgG4 is observed in mRNA vaccinated was proposed by the authors.