Estimating COVID Case Fatality Rate in Bulgaria for 2020–2021

ABSTRACT

We estimate the case fatality rate from COVID-19 with our method by age groups for three waves - September 2020 to January 2021 (wild type), February 2021 to May 2021 (alpha), and July 2021 to January 2022 (delta). We use linear regression with optimal lag with 21 days moving averaging to correct for reporting delays. We take the coefficient from the regression as the case fatality ratio. We unite the lower age groups into one to achieve a good correlation. We have new cases by age group and deaths by age group and sex. Our results indicate that the delta variant is more severe than alpha, and this is enough to outweigh any improvements in treatment since the first major wave, 14.08.2020–01.01.2021. © 2022, ICST Institute for Computer Sciences, Social Informatics and Telecommunications Engineering.