Far from being an obscure immunology topic, knowledge about the IgG4 antibody subclass (intended by nature for allergens and such) being suboptimal for immune response to a replicating virus such as Sars-Cov-2 was well known in immunology.
Even Dr. Fauci co-authored a 2015 Science Translational Medicine study that negatively spoke of IgG4 antibodies from repeat injections as undesirable in vaccine response.
Much like VAIDS, ADE, VADE and friends.
Introducing "foreign" proteins into the body is something that should be done with great care.