Rangelova, Vanya, Nevena Ivanova, Ani Kevorkyan, Sara Sariyan, and Meri Hristamyan. “ADULT VACCINATION ATTITUDES AND UPTAKES IN BULGARIA: A Cross-Sectional Study of Influenza, COVID-19, and Pneumococcal Vaccines”. PROBLEMS of Infectious and Parasitic Diseases 54, no. 2 (September 19, 2026): 5–12. Accessed September 20, 2026. https://pipd.ncipd.org/index.php/pipd/article/view/54-2-1-adult-vaccination-attitudes.