1. Worldometer (2022, November 28). Coronavirus Cases and Deaths in Spain. Worldometer. Available online: https://www.worldometers.info/coronavirus/country/spain/.
2. Trends in COVID-19 Hospital Outcomes in England before and after Vaccine Introduction, a Cohort Study;Kirwan;Nat. Commun.,2022
3. (2022, October 15). World Health Organization Coronavirus Disease (COVID-19): Vaccines. Available online: https://www.who.int/news-room/questions-and-answers/item/coronavirus-disease-(covid-19)-vaccines.
4. Popa, A.D., Enache, A.I., Popa, I.V., Antoniu, S.A., Dragomir, R.A., and Burlacu, A. (2022). Determinants of the Hesitancy toward COVID-19 Vaccination in Eastern European Countries and the Relationship with Health and Vaccine Literacy: A Literature Review. Vaccines, 10.
5. Ritchie, H., Mathieu, E., Rodés-Guirao, L., Appel, C., Giattino, C., Ortiz-Ospina, E., Hasell, J., Macdonald, B., Beltekian, D., and Roser, M. (2022, October 15). Coronavirus Pandemic (COVID-19). Available online: https://ourworldindata.org/coronavirus.