Résumé
Background: Vaccination has become increasingly relevant to prevent the global pandemic from coronavirus disease 2019 (COVID-19). Two mRNA-based emergency vaccines have recently been licensed for mass administration: BNT162b2 and mRNA-1273 COVID-19 vaccine. Delayed vaccines hypersensitivity reactions can be caused by residual proteins, or most frequently by excipients. Both mRNA vaccines contain polyethylene glycol (PEG) 2000 lipid conjugate as excipient. PEG and its derivatives with clinical cross-reactivity (polysorbates, laureth-9) are ubiquitous in many drugs. mRNA-1273 COVID-19 vaccine also contains trometamol, an organic amine used extensively. Method: We collected the patients referred to our Allergy Department with systemic skin delayed reaction after the administration of BNT162b2 or mRNA-1273 COVID-19 vaccine between January to February 2021. We recorded age, sex, personal history of allergies and previous SARS-CoV-2 infection. We describe cutaneous manifestations, latency time, treatment, and duration. We performed patch test (PT) in the upper back with PEG 400 1% in petrolatum (pet), PEG 3350 10% pet, PEG 3350 in aqueous solution (aq), PEG 4000 10% pet, polysorbate 80 1% pet, polysorbate 80 10% pet, laureth-9/ sodium lauril sulphate 1%, trometamol 0.50% aq (only in mRNA-1273 vaccinated patients), with readings at day 2 and day 4. Results: The study population comprised 11 patients: 6 (54.5%) received BNT162b2 and the rest received mRNA-1273 COVID-19 vaccine. Most patients (10/11, 90.9%) reacted to the first dose. Almost half of them (5/11, 45.4%) had detectable serum specific IgG antibodies against SARS-CoV-2 in the last 3 months. The most frequent manifestation was generalized maculopapular exanthema (6/11, 54.5%), 2 flaking palms, 1 acute generalized exanthematous pustulosis (AGEP), 1 micropapular exanthema accompanied by a 7-centimeter blister, and 1 multiple fixed drug eruption (MFDE). PT were negative in the 100% cases. We contraindicate the second dose of the vaccine in patients with severe skin reactions (MFDE, AGEP) after the first dose (2/10, 20%). The remaining patients received the second dose, reappearing systemic skin lesions in 1/8 (12.5%), having a maculopapular exanthema again. Conclusion: In our experience, mild exanthemas should not be a contraindication to receive further doses of mRNA vaccines. However, we recommended an exhaustive allergy workout in all patients with systemic skin delayed reaction.