Abstract
BACKGROUND: The coronavirus disease 2019 (COVID-19) was classified as a pandemic in March 2020 by the World Health Organization. The Pfizer-BioNTech COVID-19 vaccine was the first to be authorized in the European Union, based on data from phase 1, 2, and 3 clinical trials of limited duration. Concerns have been raised regarding the vaccine's safety profile. Some of the adverse drug reactions (ADRs) associated with vaccines may not have been identified during clinical trials. This study aimed to identify ADRs associated with the Pfizer-BioNTech vaccine in health care professionals at a Portuguese tertiary university hospital. METHODS: The data used in this analysis consist of ADRs reported through a spontaneous notification system from vaccines administered between December 27, 2020, and January 31, 2021. ADRs were categorized according to the MedDRA terminology. RESULTS: A total of 8,605 Pfizer-BioNTech vaccines were administered to 4568 health care professionals. ADRs were reported among 520 of the vaccines, with an incidence of 13.56% in women and 5.31% in men. The mean age of the population reporting ADRs was 41.52 years, with a standard deviation of 9.83 years. The most frequent ADRs were myalgia (n = 274), headache (n = 199), pyrexia (n = 164), injection site pain (n = 160), fatigue (n = 84), nausea (n = 81), chills (n = 65), lymphadenopathy (n = 64), and arthralgia (n = 53). Hypersensitivity reactions occurred in 15 health care professionals, with no anaphylactic reactions observed. A total of four Important Medical Events were observed, which consisted of two cases of syncope, one case of sudden hearing loss, and one case of transverse myelitis. CONCLUSION: The vaccine was well-tolerated among the study participants. Reactogenicity was greater after the second dose. The incidence of ADRs was higher in women and individuals aged between 40 to 49 years. Systemic adverse reactions were most frequently reported. Systematic monitoring of ADRs of COVID-19 vaccines in real-life context is essential for a more robust establishment of its safety profile.