Failure of desensitization with Pfizer-BioNTech COVID-19 vaccine in two asthmatic patients.

Since December 2020, in various countries of the world, many cases of severe allergic reactions after administration of PfizerBioNTech COVID-19 vaccine, were reported. A great concern has arisen among the doctors who administer the vaccine and the allergic patients who undergo vaccinations. In Italy guidelines were published in order to stratify the risk in the allergic population. In mRNA vaccines, the component currently suspected of causing allergic reactions is the polyethylene glycol excipient (PEG or macrogol). In patients who have shown an immediate allergic reaction to vaccine and who are negative to skin tests for PEG, desensitization with the same vaccine is proposed. In this paper we describe two cases of asthma after the first COVID vaccine administration in which desensitization has failed.