Korean Journal of Adult Nursing Vol. 34 No. 3, 249-257, June 2022 eISSN 2288-338X https://doi.org/10.7475/kjan.2022.34.3.249 INTRODUCTION The Coronavirus Disease 2019 (COVID-19) outbreak is an ongoing global pandemic. The global incidence of COVID-19 as of December 29, 2021, was 281,808,270 cases, with 5,411,759 deaths. The number of active COVID-19 cases worldwide is 30,633,650 [1]. The United States of America accounts for the highest number of COVID-19 cases at more than 100 million, followed by Europe with more than 99 million. Southeast Asia ranks third, almost surpassing 50 million cases [2]. In the Republic of Indone- sia, the number of cases had touched 4,263,433 as of Janu- ary 3, 2022, with 144,102 deaths and 4,382 active cases [3]. The high incidence of cases, morbidity, mortality, and viral mutations continue to occur, underscoring the im- portance of control efforts so that COVID-19 can be sup- pressed. The World Health Organization states that educa- tion, isolation, prevention, transmission control, and treat- ment of infected people are essential for controlling in- fectious diseases such as COVID-19 [4]. Another main area of focus is COVID-19 vaccination [1]. Safe and effective vaccines have been developed and are being administered to people worldwide [5]. A total of 8,693,832,171 vaccine doses had been administered worldwide as of December 29, 2021 [2]. The target for vaccine recipients in Indonesia is 208,265,720, with first dose vaccine coverage reaching Corresponding author: Fadlilah, Siti https://orcid.org/0000-0002-3336-3276 Nursing Programme Study Universitas Respati Yogyakarta, Kampus 2 Universitas Respati Yogyakarta, Jl. Tajem km 1,5 Maguwoharjo Depok Sleman Yogyakarta 55282 Indonesia Tel: +6285710844204, Fax: +622744437999, E-mail: sitifadlilah@respati.ac.id Received: Jan 6, 2022 / Revised: Mar 7, 2022 / Accepted: Mar 24, 2022 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. ORIGINAL ARTICLE Open Access Factors Associated with Adverse Events Following the First Dose of COVID-19 Immunization in Indonesia Fadlilah, Siti 1 · Setiawan, Deden Iwan 1 · Muflih, Muflih 1 · Amigo, Thomas Aquino Erjinyuare 1 · Susanto, Rachmat 2 · Pujianto, Ahmat 3 1 Lecturer, Nursing Programme Study of Universitas Respati Yogyakarta, Indonesia 2 Lecturer, Nursing Programme Study of Sekolah Tinggi Kesehatan Serulingmas, Indonesia 3 Lecturer, Nursing Programme Study of Universitas Borneo Tarakan, Indonesia Purpose: This study investigated the factors associated with Adverse Event Following Immunization (AEFI) for Coronavirus Disease 2019 (COVID-19) in selected areas in Indonesia. Methods: We used a cross-sectional approach with a correlational research design; a total of 2,730 samples were collected using accidental sampling. The instrument was an online questionnaire. The AEFI questionnaire was a modified version of the survey instrument of the Ministry of Health, Republic of Indonesia. x 2 and Fisher's exact tests were used for statistical analysis. Results: The most common AEFI were pain at the injection site (81.2%), drowsiness (77.2%), hunger (77.0%), headache (70.3%), and weakness (58.4%). Bivariate testing revealed that gender, age, disease history, vaccine type, and anxiety had statistically significant relationships with the incidence of weakness, pain at the injection site, and headache (p<.050). Age and vaccine type were significantly related to the incidence of fever, swelling at the injection site, and hunger. Gender, vaccine type, and anxiety were found to have statistically significant relationships with the incidence of nausea. Vaccine type and anxiety were significantly related to vomiting. Conclusion: The study found that gender, age, history of disease, vaccine type, and level of anxiety were associated with several adverse events following COVID-19 immunization. These findings provide data to nurses and other health workers to help them offer additional interventions to prevent or reduce adverse events in at-risk groups following COVID-19 vaccination. Key Words: Drug-related side effects and adverse reactions; Coronavirus; COVID-19 vaccines; Vaccination ⓒ 2022 Korean Society of Adult Nursing http://www.ana.or.kr