Impact of New Variants and Vaccines on the Course of COVID-19

Novel coronavirus disease (COVID-19), caused by Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, was first reported in December 2019 in Wuhan, China. The disease spread to many countries in a few weeks, becoming a global public health problem, and the World Health Organization declared it a pandemic on March 11, 2020. COVID-19 has caused widespread deaths worldwide, especially by causing widespread involvement in the lungs and Acute Respiratory Distress Syndrome. By 2022, the virus has infected more than 500 million people worldwide and caused more than 6 million deaths. Case fatality rates (CFR) are an important index that helps to understand the epidemiological characteristics of an epidemic. The CFR for COVID 19 is the number of deaths in COVID-19 cases divided by the total number of people infected with COVID-19. After the emergence of the disease in 2019, the CFR figures reported for COVID-19 in 2020 began to become clear. In the data coming in 2020, COVID-19 CFR values are generally reported in the range of 0.001-0.706. However, from 2019 to 2022, there were 2 major changes that could affect the CFR of the disease. The first of these is the vaccine applications developed against COVID-19. The first vaccine studies have matured by 2020 and started to be applied widely in the world in 2021. the second is the new variants of the first emerging SARS-CoV-2. In 2021, variants started to be defined and Alpha, Beta, Delta, and Omicron variants were reported as dominance variants from time to time. From 2019 to 2022, it is likely that there will be a change in the mortality of COVID-19 in relation to both the vaccines administered and the new variants emerging. Knowing the possible changes that may occur in COVID-19 mortality may cause changes in the COVID-19 measures applied all over the world. In this way, it may be possible to reduce unnecessary health costs and direct health resources to appropriate areas. The aim of this study is to determine whether there is a change in the mortality of COVID-19 from 2019, when it first appeared, to 2022. In this study, patient data were obtained retrospectively in a training and research hospital COVID-19 outpatient clinic. The obtained daily number of patients in 2020, CFR rates were compared with the number of daily patients and CFR rates in 2022. In this way, it was tested whether there was a significant difference between the year 2020, when the disease first became widespread, and 2022.