International Journal of English Literature and Social Sciences Vol-6, Issue-6; Nov-Dec, 2021 Journal Home Page Available: https://ijels.com/ Journal DOI: 10.22161/ijels Peer-Reviewed Journal IJELS-2021, 6(6), (ISSN: 2456-7620) https://dx.doi.org/10.22161/ijels.66.39 250 Adverse effects Associated with Third-Booster COVID-19 Vaccine (Heterologous Vaccines by Sinovac- Moderna) among Health Care Workers Nur Idayanti 1 , Dwi Sutiningsih 2 , Mochamad Hadi M 3 , Imam Abrori 4* 1 Master of Epidemiology, Postgraduate School, University of Diponegoro, Indonesia 2 Lecture in Epidemiology and Tropical Disease Department, Public Health Faculty, University of Diponegoro; Master of Epidemiology, Postgraduate School, Diponegoro University, Indonesia; 3 Lecture in Biology Department, Math and Science Faculty, University of Diponegoro, Indonesia 4 Port Health Quarantine Class II of Semarang, Indonesia *Corresponding author Received: 03 Nov 2021; Received in revised form: 14 Dec 2021; Accepted: 22 Dec 2021; Available online: 31 Dec 2021 ©2021 The Author(s). Published by Infogain Publication. This is an open access article under the CC BY license (https://creativecommons.org/licenses/by/4.0/). Abstract— The mRNA 1273 vaccine by Moderna © has recorded to be94.1% effective against laboratory- confirmed Covid-19 infection. Health care workers in Indonesia are receiving third-booster vaccine by Moderna after the two doses of virus-inactivated vaccine. Further evaluation of Covid-19 mRNA vaccine post-injection effects on health care workers is necessary. This present study asssessed the post- immunization adverse events tohealth care workersin the Port Health Office of Semarang.This was a retrospective, cross-sectional, observational study aimed to the HCWs, both staff and non-staff, of the Port Health Office of Semarang.We identified and analyzed the adverse effects on 132 workers who had been receiving third-mRNA booster vaccine by Moderna. About 37.8% (50 out of 132)respondents experienced adverse events after receiving third-booster vaccine by Moderna. Among them, female workers (62%) had more incidents compared to males (38%). the most common symptoms were localized painon injected arm (100%), fatigue (44%), fever (42%), myalgia (38%), and chills (30%). Other symptoms like night sleep issue, diarrhea, nausea, an headacheswere also reported.The mRNA 1273 vaccine by Moderna © injection as booster provides several severe but not life-threatening symptoms, most of the emerging cases are fatigue and fever and and possibly correlated with gender. Keywords— SARS-CoV-2,adverse effects, heterologous vaccine. I. INTRODUCTION Globally,the coronavirus disease (Covid-19) has been reported to reach more than 239 million patients and hada mortality of 4.8 million (case fatality rate: 2.03%) as of mid October 2021. At the same period, Indonesia recorded 4,231,046 patients and 142,811 deaths (CFR 3.34%). According to the Covid-19 case report (the 19 th week of 2021), Central Java province had a worse proportioncases in health care workers (HCWs) 2.9%. [1,2] Indonesian national government responded the vulnerable situation of HCWs the instruction to apply third-booster vaccination using the mRNA 1273 vaccine by Moderna © after primer vaccination with inactive vaccine (booster with heterologous vaccines) .The strategy was based on a positive record of Moderna vaccine that reaches 94.1% effectiveness and is listed in the Emergency Use Listing (UEL) by WHO since April 30, 2021. [3] Indonesia reported the mild effects of the vaccine emerged by recipients of the third-booster vaccine. [4] Kadali et al. had performed an investigation against the identical vaccine to 432 post-vaccinated people.Various reponses from the respondents are the following: 25% had