It was initially thought that PEG is the likely culprit for the allergic reactions seen in mRNA Covid vaccines. It turns out that Intradermal skin testing to PEG has limited utility in evaluating this anaphylaxis and that most severe postvaccination allergic symptoms are not caused by hypersensitivity to PEG.
A vaccine registry study from a single health system found that 86.7% tolerated a second dose when given under allergy clinic observation with antihistamine pre-treatment, and that PEG testing and challenges were not helpful, with a large number of false positives. (Ann Allergy Asthma Immunol, October 23, 2021)
In this cohort study of 52,998 healthcare workers at the Massachusetts General Brigham Health System, self-reported high-risk allergy history was associated with an increased risk of self-reported allergic reactions after mRNA COVID-19 vaccination, but following the CDC guidelines, with allergist consultation, risk stratification, and shared decision-making, all employees were able to complete the 2-dose vaccine series. (JAMA Netw Open, October 26, 2021)
It turns out that most people with reaction to the initial mRNA vaccine can be safely revaccinated. However, you should seek proper evaluation with an qualified Allergist/Immunologist.
