Is Omicron A “Vaccine-Escape” Variant?

How Can We Know What Kind Of Breakthrough Infections Omicron Produces?

At the end of my previous post on breakthrough infections I suggested that there are in fact very good reasons to believe that the Omicron variant is not creating “dangerous” (to the patient) breakthrough infections, that is, it is not creating “Type 1 breakthrough infections”, in the typology that I set out in that post. The ability to create Type 1 breakthrough infections would make a variant very dangerous, because an infection by such a variant would evade vaccine-primed human immunity, and the patient’s immune system would have to start from scratch on the time-consuming process of learning to identify the virus, and to create the armament of antibodies and immune cells to fight it without the assistance of a vaccine. The “Type 3” breakthroughs (whether of the “false breakthrough” or “semi-breakthrough” sub-types) are much less dangerous. Neither sub-type actually evades vaccine-primed immune response: they merely appear to, because the rapid reproduction of the virus in the body leads to measurable, often infective levels of viral load despite neutralizing antibodies’ efforts to restrain that growth; but the infection’s early doom is already sealed, because the cellular part of the adaptive immune system—specifically the killer T-cells—are on their way, and will wipe it out in short order. So while the infected individual may be infective (Type 3b), he or she is not usually at risk of severe disease.

This is an orderly proceeding for an immune response to an infection, incidentally. Neutralizing antibodies are only the first layer of the adaptive immune system, and despite their prominence in media discussion of vaccines and therapies they are not responsible for either preventing severe disease or clearing an infection. Antibodies merely slow down the rate of growth of the infection, buying time for the real heavy hitters—the T-Cells—to be mobilized to fight off the infection. That’s the key difference between Type 1 and Type 3: if a variant can create Type 1 breakthroughs, the T-Cells can’t fight it, whereas if it can only create Type 3 breakthroughs, the T-Cells will kick the crap out of it.

So it actually matters what kind of breakthrough infections Omicron is producing, and that’s the reason I’m trying to create some badly-needed clarity in the discussion surrounding the wretchedly ill-chosen term “breakthrough”. What, then, is the evidence that Omicron is not a Vaccine Escape Variant of Concern?