Adverse Effects Associated with the First Dose of the Pfizer–BioNTech COVID-19 Vaccine in Healthcare Workers from Mexico: A Case Serie from Passive Surveillance

Almost a year after the declaration of the pandemic due to the SARS-CoV-2 virus which causes the COVID-19 disease and the need to contain the progression and treatment, the promising option was designing an effective and safe vaccine to reach a state of massive immunity. The first vaccine approved was the one produced by Pfizer–BioNTech, and its application started in December 2020. Within days of the first applications, 0.2% of adverse events were reported. Herein, a series of 26 cases with the manifestation of adverse events related to the application of the first dose of the BNT162b2 vaccine from Pfizer–BioNTech in healthcare workers from Mexico. Of these cases, only five patients were classified with a certainty of anaphylaxis; two of them presented seizures, and their management is described individually. After the examination of all the cases, the symptoms were resolved. In Mexico and around the globe, the vaccination process continues, and the report of possible AEFIs is still needed to contribute to the pharmacovigilance of this new vaccine and improve its safety profile.