Answers to burning questions for clinical allergologists related to the new COVID-19 vaccines.

Background: Along with the newly approved vaccines against coronavirus disease 2019 (COVID-19), first reports of allergic or intolerance reactions were published. Subsequently, questions arose whether these vaccines pose an increased risk for intolerance reactions and whether allergic patients may be at higher risk for this.

Results: Allergic reactions following COVID-19 vaccinations have been reported, but mostly of mild severity and at normal (Moderna®) or only slightly increased frequency (BioNTech/Pfizer®) compared to established conventional vaccines. The risk of allergic reaction to the newly licensed vector vaccines (AstraZeneca®, Johnson&Johnson®) cannot be conclusively assessed yet, but also appears to be low. There is currently no evidence that patients with allergic diseases (atopic patients) react more frequently or more severely to these vaccines. It is currently assumed that intolerance reactions of the immediate-type are either type I allergic (IgE-mediated) reactions or occur via complement activation (CARPA, "complement activation-related pseudoallergy"). Polyethylene glycol (PEG) or polysorbate, which are present as stabilizers in the vaccines, are suspected as triggers for this.

Conclusion: The data available so far do not show a significantly increased risk of immediate-type allergic reactions in atopic persons. In almost all cases, atopic patients can be vaccinated without problems. Standardized follow-up tests after suspected allergic reactions or CARPA-mediated reactions are currently limited.