Side Effects Related to BNT162b2 and CoronaVac Vaccine Requiring Emergency Department Visit.

 Currently, the most effective method in the fight against coronavirus disease 2019 (COVID-19) is vaccination against the disease. However, there are hesitations among society concerning the safety and side effects of COVID-19 vaccines. We aimed to determine the observed side effects that require an emergency room visit after taking the BNT162b2 and CoronaVac vaccines.  This prospective observational study was conducted with patients who presented to the emergency department due to vaccine-related complications after COVID-19 vaccination. The patients' symptoms at the time of presentation, time from vaccination to the onset of symptoms, and dose of the vaccine administered were determined. In addition, the demographic characteristics of the patients, whether they had a history of COVID-19 infection, and their vital signs at the time of presentation were recorded. The variables were compared according to the type of vaccine administered.  The study included 182 patients who presented to the emergency department over a 6-month period. It was determined that 166 of these patients (91.2%) had received the BNT162b2 vaccine and 16 (8.8%) had received the CoronaVac vaccine. The majority of the patients did not have a history of COVID-19 infection (70.3%), and most presented to the hospital with complications after the second dose (61%). The onset of vaccine-related symptoms was mostly within 1 to 12 hours (39%). The majority of patients (97.8%) were discharged from the emergency department. The most common symptoms after vaccination were fatigue (  = 70), followed by muscle/joint pain (  = 52), headache (  = 33), and fever (  = 32). The rate of dizziness was found to be statistically significantly higher in the CoronaVac vaccine group than in the BNT162b2 vaccine group (  = 0.008). There was no statistically significant difference between the two vaccine groups in relation to the remaining symptoms (  > 0.005).  There were no serious complications related to the BNT162b2 or CoronaVac vaccine. The most common symptom after both vaccines was fatigue; therefore, the BNT162b2 and CoronaVac vaccines can be safely administered.