Retrospective Study for Identificatiopn of a Link Between Doxycycline and COVID-19 Treatment

DOXY-COVID study is a national, observational, retrospective cohort study to compare the risk of severe COVID-19 in doxycycline-treated patients versus non-doxycycline-treated control patients (so-called case-cohort study). The patient inclusion period corresponds to the main waves associated with the COVID-19 epidemic in France, i.e. from January 1, 2020 to November 30, 2021. Indeed, the time of data access, expected during 2022, would not allow reasonable follow-up of doxycycline-exposed patients from December 1, 2021. Data of interest collected on these patients are requested over the period from January 1, 2016, through December 31, 2021: * From January 1, 2016, in order to be able to define a pre-exposure phenotype over a follow-up period of at least 4 years in the French Health Insurance databases (period 2016-2019 inclusive) * Until December 31, 2021, in order to have at least one month's hindsight on the risk of occurrence of severe forms of COVID-19