Adverse Events Following Immunisation of COVID-19 Vaccine at Queen Elizabeth Hospital Lim Ming Yao1, Lem Fui Fui1 1Clinical Research Centre, Queen Elizabeth Hospital P-79 NMRR NO: NMRR-21-713-59282 Introduction The COVID-19 pandemic has brought about catastrophic repercussions globally. First discovered in 2019, as of July 2021, this vicious virus has resulted in more than 193 million people being infected and more than 4 million mortality cases worldwide[1]. Apart from the many innocent lives lost, the global economy has contracted by 3.5% in April 2021 according to a report published by the International Monetary Fund[2]. While public health measures have been devised by experts in every country with the intent of curbing the spread of the virus, these measures inevitably involve temporary cessation of many economic activities which in turn affected the livelihoods of the people. Locally, in Malaysia, the unemployment rate in 2021 remains at a staggering rate of 4.5% according to official figures. The fundamental solution to this natural calamity is herd immunity made possible by the development of vaccine against this virus. This impetus to seek out effective vaccines has brought together leading scientists and institutions around the world[3]. With these concerted efforts, many vaccines were being tested and the development process has been expedited at a speed unprecedented in the human history. Traditionally, it takes 10-15 years for the development of a safe vaccine. Nonetheless, in dealing with this callous virus, time is a luxury that we do not have. As a result, many uncertainties remain unveiled regarding the safety and long term efficacy of vaccine developed in such hasty fashion. In Malaysia, front liners are among the first to be vaccinated. In this study, we aim to describe and summarise adverse events following immunisation (AEFI) using Pfizer Comirnaty vaccine as reported by healthcare workers in the hospital setting. Method The AEFI data were collected via three routes. Firstly, at the observation zone immediately post vaccination. Secondly, when the patient visits emergency department of Queen Elizabeth Hospital. Thirdly, information collected on the mySejahtera app. The data were then collated from these ADR forms for the purpose of this study over the period from 2nd March 2021 to 9th June 2021. Results Out of 155 subjects recruited, there were 80.6% female, in contrast with the 19.4% male. The median age were 33 year old. 64.5% of them reported history of allergy. The five most commonly reported adverse events were rashes (27.7%), globus pharyngeus (27.1%), dizziness (25.8%), pruritus (23.2%) and nausea (16.8%). 86.5% of the subject required treatment and the two most commonly administered treatment are intravenous steroid and intravenous antihistamines. 65% of the subject reported history of allergy whereas 28% and 35% reported drug allergy and food allergy respectively. Discussion Gender preponderance among female have also been reported studies conducted in Korea [4] and Italy [5]. In terms of frequency of reported adverse events, rashes and fever were also listed as common events in another study done in Italy [6]. In USA, thrombocytopenia cases were reported, in our study, however, we did not capture any cases of bleeding tendency which could be suggestive of thrombocytopenia. However, ethnic differences in response to treatments due to biologic factors, such as genetic and epigenetic variants [7] , may contradict the findings of thrombocytopenia [8] where the majority of the data is from the Scottish population[9]. Rashes are the most prevalent adverse effects, according to Robinson et al., (2021), who found that Asians are the second most afflicted which is aligned with our findings [10]. There are several limitations to our study. Firstly, report bias, those who experience mild symptoms that resolved spontaneously and did not seek treatment at hospital might not report it to the app and hence not