COVID-19 vaccine
Despite the high safety profile of COVID-19 vaccines, shortly after the start of the vaccination campaign, global health authorities, acting correctly in an overcautious way, had to contraindicate these vaccines among patients with a history of immediate allergic reaction to the first dose of the vaccine or to any of the vaccine excipients, polyethylene glycol (PEG) in mRNA vaccines and PS80 in adenovirus vector vaccines47,48. Thus, in an effort to provide guidance, skin tests for individuals with PEG/PS80 allergy or a reported allergic reaction to a prior vaccine dose were recommended49. Nowadays, instead, increasingly numerous data permit to refute the hypothesis that excipient skin testing could help to manage such patients not impacting tolerance of a second dose and that persons with first dose reactions can safely be re-vaccinated50. The aetiology of anaphylaxis in these cases is not fully understood and is still an open area of active research. To note, in contrast to what would be expected in regards to a suspicion for an allergic IgE-mediated pathogenesis, reporting rate of anaphylaxis was higher after the first dose then after the second dose and it might be possible that a non-IgE mediated mechanism could be implicated, such as complement activation13.