1. Centers for Disease Control and Prevention. Global immunization, https://www.cdc.gov/globalhealth/immunization/ [accessed 10 February 2022].
2. Centers for Disease Control and Prevention. Measles (Rubeola), https://www.cdc.gov/measles/cases-outbreaks.html [accessed 10 February 2022].
3. European Centre for Disease Prevention and Control. COVID-19 vaccine tracker, https://vaccinetracker.ecdc.europa.eu/public/extensions/COVID-19/vaccine-tracker.html#target-group-tab [accessed 10 February 2022].
4. Hepatitis A outbreak among MSM in Berlin due to low vaccination coverage: epidemiology, management, and successful interventions;Zimmermann;Int J Infect Dis,2021
5. Immunization of health-care providers: necessity and public health policies;Maltezou;Healthcare,2016