In a nutshell, you administer something intended to increase antigenicity. What could go wrong?
The discussion of adverse reactions in paragraphs one and two of your post tacitly assumes the reactions are prompt and consistent. If so, no problem, the system works. This may not always be true. If adjuvants could cause antigenicity to lets say hundreds of thousands of self epitopes which somehow were not properly eliminated during the time the immune system was eliminating memory cells carrying receptors which matched self protein epitopes. In this case, there would not be a sufficient cluster of the same AE to prove the association.
Also autoimmune diseases often develop slowlover decades before they become severe, and are very often not reported, not diagnosed, or misdiagnosed.
My comments were not pointed at Novavax or even this adjuvant in particular. I conjecture that adjuvants ( perhaps only some) are responsible ( in part)ii for the epidemic of strange autoimmune diseases and chronic undiagnosed conditions in America.
As I posted once before ( with some edits) There is probably an autoimmune disease for every kind of tissue in the body. The old Medical Mysteries show had some suffering person in almost every episode ( three different mysteries per episode) who spent decades and went through many doctors to finally find out they had an autoimmune disease attacking either their arterial epithelium, their nerve cell sheath, cartilage, ureter, etc etc, in almost every episode. These rare autoimmune diseases were finally diagnosed by a researcher or second or third level specialist.
It is likely vaccine adjuvants cause ( or prime) people to develop autoimmune disease, but the autoimmune diseases are so many and varied, so difficult to diagnose, frequently have sporadic symptoms related to stress, etc, and often take so long to show up, that causation by a vaccination can’t be proven. This is the mechanism by which anthrax vaccinations during the Gulf War in the 90s are suggested to have caused the amorphous cluster of diseases called Gulf War Syndrome.
Infections sometimes trigger autoimmune disease. So does stress. Something happens whereby self proteins previously tolerated become confused with non-self. It would be surprising if adjuvants didn’t.
I went through progressively worsening allergies in early adulthood. The usual antiallergy remedies kept me going for years but did not prevent the eventual collapse of my health to the point of near disability. Finally, I figured out that the root cause was celiac disease, with a gluten free diet and vitamin and mineral supplements restoring my health.
Yet, even at the worst when it seemed that almost anything could trigger an allergy attack, never once did I get anything but a sore arm for a day or so from the occasional routine vaccine. Even when I could not stand being around new clothes in a store for more than a few minutes because the sizing and dyes triggered sneezing, tears, and my eyes closing shut, I could still tolerate being vaccinated.
Are adjuvants and vaccines always utterly safe for everyone? Of course not, but in the aggregate, the odds are heavily in favor of their safety and effectiveness when developed and used properly. In the balance between disease burden and vaccine risk, a vaccine is usually the best choice, with everyone free to make the decision for themselves.