Study on the adverse events following immunization (AEFI) of ChAdOx1 nCoV-19 vaccine in a group of Sri Lankan medical officers
Authors: Jayatilake JAMA , Karunaratne HMAH , Perera KYD , Dissanayake Y , Dileka WSC , Weerasinghe IE , Jayatilake JAMS 
Published: April 2022

Introduction: Amidst a rapid outbreak of COVID-19, ChAdOx1 nCoV-19 vaccine was initially administered to health care workers in Sri Lanka.Objective: The aim of this study was to investigate adverse events following immunization (AEFI) after the first dose of ChAdOx1 nCoV-19 vaccine in a group of Sri Lankan medical officers from 5th February to 7th March 2021.Methods: A retrospective survey was conducted using a pretested Google form questionnaire designed to gather demographic data, medical history, AEFI and their management. The questionnaire was shared among a convenience sample of medical officers through online apps (Facebook, Imo, Viber, WhatsApp). Responses to the questionnaire were collected and the quantitative and categorical data and their associations were analyzed statistically.Results: Of 836 participants (male/female ratio = 0.92; mean age = 39.6±7.9 years), the majority, 738 (88.3%) experienced AEFI. Commonest AEFI were body ache (80.7%), lethargy (76.1%), local site reactions (72.4%) fever (70.1%), chills (68.7%) and headache (61.5%). The most severe AEFI was body ache (35.6%). The mean time of onset of AEFI was 11.3±7.5 hrs. AEFI lasted for a mean duration of 36.3±24.3 hrs. Occurrence of AEFI was significantly associated with age and, individuals below 40 years were more likely to experience AEFI (Pearson Chi-Square =5.13; P=0.02). Moderate to severe AEFI was also significantly associated with age where a high proportion of younger individuals (≤40 years) experienced moderate to severe AEFI (Pearson Chi-Square 5.31, P=0.02). A proportion of females (80.7%) had AEFI. The occurrence of AEFI was significantly associated with the females (Pearson Chi-Square 10.34, P=0.01).  A significant association between poor physical exercise and the incidence of AEFI (Pearson Chi-Square 11.15, P=0.004) was also observed. Those who had no regular exercise (79%) were more prone to get AEFI than those who had regular exercise (72.5%). Paracetamol was used prophylactically by 56.1% vaccinees prior to vaccination. Paracetamol was taken by 52.8% vaccinees (1g, 6-8 hourly for 2-3 days) therapeutically for AEFI as self-medication. However, 4 (0.005%) sought medical advice on further management and 7 (0.008%) got hospitalized.Conclusions: A high incidence (88%) of AEFI was observed in our study population. The commonest AEFI were body ache, lethargy, local site reactions, fever, chills and headache, while the most severe AEFI was body ache. AEFI associated in ChAdOx1 nCoV-19 vaccine lasted about 1-2 days. Occurrence of AEFI was significantly associated with females below 40 years and with low physical exercise. The majority took self medication with paracetamol either prophylactically or therapeutically. Medical consultation and hospitalization for AEFI were low. AEFI of ChAdOx1 nCoV-19 vaccine was observed to be tolerable and responded to self medication with paracetamol. Surveillance studies on AEFI are feasible using online apps.