The Covid Shot, the IgG4 Switch & the Cancer Question
What the New Wave of Studies Is (and Isn’t) Telling Us
File this under “things we were told couldn’t happen.”
Over the last two years, scattered lab findings and case reports have started to rhyme: repeated mRNA exposure appears to nudge antibody profiles toward IgG4, a “stand-down” subclass associated with tolerance rather than attack.
IgG4 is a type of antibody that tells the immune system to calm down instead of fight. So instead of attacking something it sees as a threat, it signals the body to “stand down” — to tolerate that substance rather than launch an inflammatory response against it.
In parallel, cancer biologists are asking an uncomfortable question: could chronic spike exposure and/or product impurities plausibly tip some patients toward immune dysfunction that allows cancers to accelerate?
This isn’t a gotcha. It’s a we-should-look.
Below I’ll walk through (1) the newest IgG4 paper making the rounds, (2) what peer-reviewed data actually show on class switching, (3) the “17 mechanisms” cancer thread and what’s signal vs. speculation, and (4) why the right next step is rigorous, de-politicized research—not censorship or triumphalism. Along the way I’ll quote directly from the sources so you can see the claims in their own words.
1) The new IgG4 preprint everyone’s sharing
Adam Gaertner highlighted a University of Amsterdam–led study following kidney-disease cohorts who’d received ≥2 mRNA doses. The headline: over 2–6 months post-series, spike-specific IgG4 rose while IgG2/IgG3 waned; IgG1 remained relatively stable. Gaertner’s gloss is blunt: “after a long delay… the immune response in mRNA vaccinees eventually switches to the non-inflammatory IgG4 subclass.” veryvirology.substack.com
The preprint he points to (and related work in this vein) does indeed report a relative tilt toward IgG4 with repeated exposure. A separate October 2025 medRxiv manuscript reports a significant increase in IgG4:IgG1 over time, again consistent with class-switching toward tolerance after repeated antigen exposure. MedRxiv
Key nuance: “switch” here is usually partial, not absolute. That matters. In classic allergy desensitization, more IgG4 can be a feature, not a bug. In viral defense, too much “peace signal” at the wrong time could be unhelpful. What the field is sorting out now is where on that spectrum these COVID exposures land for different people.
