Michael Abel AlaoBabatunde Oluwatosin OgunbosiOlayinka Rasheed IbrahimRegina Eziuka OladokunIkeoluwa Abiola Lagunju2025-02-182025-02-182022-09-1210.60787/NMJ-63-3-46https://dspace.ughe.org/handle/123456789/228Background: Vaccination has been described as the most critical tool to end the COVID-19 pandemic and to save lives and livelihoods. This study aimed to evaluate the spectrum of adverse events following immunization with the COVID-19 AstraZeneca/Oxford vaccine in Ibadan, south western Nigeria. Methodology: Across-sectional study. Adults aged ≥ 18 years who had received the Astra-Zeneca/Oxford COVID-19 vaccine at selected COVID-19 vaccination centres across three Local Government Areas in Ibadan, SW Nigeria were interviewed by means of a structured questionnaire to determine the spectrum of adverse events following immunisation (AEFI). Results: We enrolled 369 adults; 179 males and 190 females, with a mean of age of37.8±12.0 years.Three hundred and thirty two (90.0%) ofthe subjects experienced one or more AEFI. Ofthe total AEFIs reported, the most frequent were headache 225 (21.1%), fatigue/tiredness 186 (17.4%), pain at the injection site 99 (9.3%) and myalgia 97(9.1%). Nine in ten (96.4%) of these AEFIs occurred within 48 hours postvaccination.Higher severity of adverse events score (p=0.049) and multiple AEFIs (p=0.01) were associated with the first dose of the vaccine. There were severe AEFI in 1.2% (95% CI: 0.3-.9.0%) of the respondents. Presumed or confirmed COVID 19 infection before vaccination increased the odds of AEFI (OR 7.0, 95% CI: 1.8-27.8). Conclusion: Our study showed a high frequency of AEFI among recipients of the Astra Zenecca/Oxford vaccine in Ibadan. Majority of the AEFIs are mild and self-limiting.Previous infection with COVID-19 appears to increase the risk ofAEFI. Keywords: COVID-19; Vaccine; Adverse event following immunization; Severe Acute Respiratory Syndrome Coronavirus 2; AstraZeneca/Oxford COIVD-19 Vaccine.enCOVID-19VaccineCoronavirusAstraZenecaNigeriatext::journal::journal article