1. World Health Organization/Europe. Coronavirus disease (COVID-19) outbreak - WHO announces COVID-19 outbreak a pandemic. https://www.euro.who.int/en/health-topics/health-emergencies/coronavirus-covid-19/news/news/2020/3/who-announces-covid-19-outbreak-a-pandemic. Accessed 13 March 2022.
2. European Centre for Disease Prevention and Control. SARS-CoV-2 variants of concern as of 27 January 2022. https://www.ecdc.europa.eu/en/covid-19/variants-concern. Accessed 29 January 2022.
3. Bundesministerium für Gesundheit. Impfdashboard. https://impfdashboard.de/. Accessed 29 January 2022.
4. COVID-19 Schweiz,2022
5. Gesundheit, Pflege und Konsumentenschutz,2022