What is the stabilizing agent in the Pfizer and moderna vaccines?
Precise cause and effect haven’t been isolated at this time, but the working theory is that it’s polyethylene glycol, which is also commonly used in foods, cosmetics, and other medications. However, it’s been show to cause rare allergic reactions in previous use cases.
The differences in how PEG is used in the Moderna and Pfizer lipid shell formulations likely accounts for the variance in reaction frequency (1 per 90,000 with Pfizer, 1 per 400,000 with Moderna).