EVALUATION OF THE EFFECTIVENESS OF ROTAVIRUS VACCINE FOLLOWING THE IMPLEMENTATION OF THE NATIONAL ROTAVIRUS VACCINATION PROGRAM IN BULGARIA

INTRODUCTION: Rotaviruses are a leading cause of infectious diarrhea in infants and children up to 5 years of age. Their widespread distribution, high morbidity, and mortality define them as a disease of significant public health and social importance. AIM: To study the effectiveness of the rotavirus vaccine after the introduction of the National Program for Vaccination against Rotaviruses in the Republic of Bulgaria for the period 2014–2023. MATERIALS AND METHODS: Data from the national registration of communicable diseases in Bulgaria, published in the official reports of the National Center of Infectious and Parasitic Diseases (NCIPD) for the period 2014–2023, and data from the official websites of WHO and ECDC were analyzed. Documentary, epidemiological, descriptive, and mathematical-statistical methods were used for processing the obtained results. RESULTS: During the period 2014–2023, rotaviruses ranked second (11%) after enterocolitis (81%) in the structure of intestinal infectious diseases in the Republic of Bulgaria, reaching the highest morbidity rate in 2017 – 40.52‰. With the introduction of the National Program for Control and Treatment of Rotavirus Gastroenteritis 2017–2021 in the country, free recommended rotavirus vaccines have been provided to all newborns. In the period 2017–2023, a significant increase in immunization coverage of newborns has been observed, reaching from 17.9% in 2017 to 43% in 2023. A high correlation is reported between the number of immunized children and the number of cases (r = –0.74), as during the same period the morbidity rate of RGE decreased significantly to 9.72‰ in 2023. CONCLUSION: With the increase in immunization coverage with rotavirus vaccines in children during 2017–2023, a significant reduction in morbidity from RGE was observed, which clearly demonstrates the effectiveness of the rotavirus vaccine.