In most adverse reactions, the problem is not the adjuvant but that an abnormally sensitive individual has reacted badly to the antigen or to chicken egg protein that has slipped though the antigen purification process.
Novavax is highly regarded by many medical experts because it is pioneering a new and better method of vaccine production that relies on identifying key antigens from a pathogen, producing those antigens quickly and in abundance using not chicken eggs but genetically modified insect bacteria, and then adding its mild, plant based adjuvant with a favorable safety profile to finish the vaccine.
In concept at least, this should result in vaccines that are safer because they have a reduced risk of adverse reactions.
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.