mRNA-based COVID-19 vaccines such as BNT162b2 have recently been a target of anti-vaccination campaigns due to their novelty in the healthcare industry; nevertheless, these vaccines have exhibited excellent results in terms of efficacy and safety. As a consequence, they acquired the first approvals from drug regulators and were deployed at a large scale among priority groups, including healthcare workers. This phase IV study was designed as a nationwide cross-sectional survey to evaluate the post-vaccination side effects among healthcare workers in Slovakia. The study used a validated self-administered questionnaire that inquired about participants' demographic information, medical anamneses, COVID-19-related anamnesis, and local, systemic, oral, and skin-related side effects following receiving the BNT162b2 vaccine. A total of 522 participants were included in this study, of whom 77% were females, 55.7% were aged between 31 and 54 years, and 41.6% were from Banska Bystrica. Most of the participants (91.6%) reported at least one side effect. Injection site pain (85.2%) was the most common local side effect, while fatigue (54.2%), headache (34.3%), muscle pain (28.4%), and chills (26.4%) were the most common systemic side effects. The reported side effects were of a mild nature (99.6%) that did not require medical attention and a short duration, as most of them (90.4%) were resolved within three days. Females and young adults were more likely to report post-vaccination side effects; such a finding is also consistent with what was previously reported by other phase IV studies worldwide. The role of chronic illnesses and medical treatments in post-vaccination side effect incidence and intensity requires further robust investigation among large population groups.

Clinic of Otorhinolaryngology and Head and Neck Surgery Central Military Hospital and Faculty Hospital 034 26 Ružomberok Slovakia

Czech National Centre for Evidence Based Healthcare and Knowledge Translation Institute of Biostatistics and Analyses Faculty of Medicine Masaryk University 625 00 Brno Czech Republic

Department of Anesthesiology F D Roosevelt University Hospital 975 17 Banska Bystrica Slovakia

Department of Maxillofacial Surgery F D Roosevelt University Hospital 975 17 Banska Bystrica Slovakia

Department of Prosthetic Dentistry Faculty of Medicine and Dentistry Palacky University 775 15 Olomouc Czech Republic

Department of Public Health Faculty of Medicine Masaryk University 625 00 Brno Czech Republic

Institute of Health Information and Statistics of the Czech Republic Palackého náměstí 4 128 01 Prague Czech Republic

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