The purpose of this study is to learn about: * effects of living with COVID-19 and * how effective is nirmatrelvir-ritonavir in treating COVID-19. This is a study of two groups of COVID-19 patients in Taiwan. In Group 1 the below participants were included in the study: * Patients of all ages. * Patients who were confirmed to have COVID-19 infection between 01 January 2021 and 31 December 2021. * Cases of patients registered in the databases. In Group 2 the below participants were included in the study: * Participants who are 12 years or older. * Confirmed to have COVID-19 between 01 January 2022 and 31 December 2022. Nirmatrelvir-ritonavir is taken by mouth and is used to treat COVID-19. The study will look at: * the nature of Covid-19 disease. * as well as the experiences of people receiving the nirmatrelvir-ritonavir. This study will help to: * understand what type of patients will need to be admitted to hospitals. * see severe results due to COVID 19 infection. * have more knowledge on the use of nirmatrelvir/ritonavir on COVID-19.