Purpose To evaluate the occurrence, extent, and severity of adverse reactions associated with the vaccine of COVID-19 (ChAdOx1 nCoV-19 vaccine or AstraZeneca) among Kabul University of Medical Sciences staff. Patients and Methods A retrospective observational, interview-based study was conducted from 4 to 20 April, 2021, to evaluate the adverse reactions associated with the vaccine of COVID-19 (ChAdOx1 nCoV-19 vaccine or AstraZeneca) among the staff and lecturers of the Kabul University of Medical Sciences, Kabul, Afghanistan. Participants were interviewed following the administration of the first dose of the AstraZeneca vaccines. They were asked to report any adverse reactions that occurred within 8–10 days after vaccination. The frequency, duration, severity, and outcome of the reactions were recorded. Association of the adverse reactions was analysed with the ages of participants and previous infection with SARS CoV-2. Results The most common adverse reactions reported by the participants were muscle pain (68.3%), local pain (58.8%) at the site of injection (68.3%), fever (66.3%) and fatigue (66.3%). Almost half of the respondents reported chills, joint pain and headache after receiving the first shot of the vaccine. The frequency of adverse reactions was higher in participants aged 40 years or less, and in those previously infected with SARS CoV-2. The severity of most adverse reactions was mild to moderate. No serious case or death was reported. Conclusion The adverse reactions reported by the participants were mild to moderate in severity, and for a short duration. The findings of this study help us to address the vaccine hesitancy caused by worries about severe adverse effects associated with the COVID-19 vaccine.