One of the biggest misunderstandings in public discourse is the idea that immunity is binary: either you respond or you don’t. In reality, the immune system is constantly making decisions. Should it escalate? Or should it stand down?
Antibodies are a good way to understand this. Some antibodies are designed to attack aggressively, activating immune cells and driving clearance. Others exist specifically to reduce immune responses—to prevent damage when an antigen is judged to be familiar or non-threatening.
One of those antibodies is IgG4.
IgG4 is not a “bad” antibody. In fact, it plays an important role in tolerance—particularly in allergy medicine, where it helps the immune system stop overreacting. But tolerance is context-dependent. It works well for pollen. It is far less helpful for a virus that enters through the airway, infects cells, and continues to evolve.
A signal we should not ignore
Over the past few years, several studies—including a recent detailed analysis from Australia—have shown something striking: repeated mRNA exposure to SARS-CoV-2 spike protein can drive a marked shift toward IgG4 antibodies in a subset of people.
Not everyone. But some.
In these individuals, IgG4 doesn’t just rise slightly—it can become a dominant proportion of their spike-specific antibodies. At the same time, the more aggressive IgG1 antibodies, which are needed for effective viral clearance, decline.
The result is an immune response that still binds the virus, but does so in a way that tells the immune system to stay calm.
That matters.
Because when IgG4 binds to the virus, it signals:
“This antigen is not dangerous. Do not escalate.”
That may protect against excessive inflammation. But it may also impair viral clearance.
Why lack of symptoms is not always reassuring
I’ve spoken to many people who say, “I’ve had multiple boosters and I’ve never had COVID.” On the surface, that sounds reassuring. But biologically, it raises another possibility.
If someone has repeated exposure to a virus that is circulating everywhere, yet mounts no reaction at all—no fever, no sore throat, no immune symptoms—one has to ask whether they are truly avoiding infection, or whether their immune system has simply stopped responding to it.
In the IgG4-dominant state, infection may still occur, but without the inflammatory signals we typically associate with illness. The virus can replicate quietly in the upper airway, potentially for longer periods, without triggering a strong clearance response.
This is not immunity in the traditional sense. It is tolerance.
The mucosal problem we keep overlooking
Respiratory viruses are best controlled at the mucosal surface—before they enter cells. That role belongs primarily to secretory IgA, not IgG antibodies. Certainly not IgG4!
Intramuscular vaccination, does not reliably generate durable mucosal IgA. Instead, what we increasingly see in saliva is IgG antibodies, largely leaking in from the bloodstream.
When that IgG is skewed toward IgG4, the message at the mucosal surface becomes even quieter.
Binding without clearance. Recognition without urgency.
A population-level consequence
If a meaningful subset of the population enters a tolerance-dominant immune state, where the virus is recognised but not efficiently cleared, then persistent viral circulation becomes inevitable. Not because the virus is unbeatable, but because the immune system has adapted in a way that prioritises calm over clearance.
This doesn’t produce dramatic collapse. It produces something more subtle:
frequent reinfections
low-grade or unnoticed illness
ongoing transmission
and, in some people, prolonged immune dysregulation
And because these individuals don’t get very sick, the problem stays invisible.
This reflects how the immune system behaves under repeated, non-sterilising exposure to a persistent antigen.
But biology doesn’t care about narratives. If we train the immune system to tolerate a virus that continues to infect and evolve, we shouldn’t be surprised when it keeps circulating.
The question we should now be asking is not “Why are people still catching COVID?”
It is:
“Have we unintentionally taught some immune systems to stop fighting it?”
That is a question worth confronting—carefully, honestly, and without fear—but it is one we can no longer afford to ignore.
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