The effect of preventive vaccination on chickenpox incidence in Russia

Abstract

Introduction. The significance of the chickenpox (CP) problem for public health and economy of Russia necessitated inclusion of CP vaccination in the regional immunization programs of some regions of the Russian Federation and in the vaccination schedule as an epidemic-response measure. The purpose of the study was to assess the effectiveness of CP vaccination to provide the rationale for recommendations on expansion of the national preventive vaccination schedule. Materials and methods. The vaccination effectiveness was assessed by comparison of the vaccination rates and CP incidence rates in 20062021 with the reference to the data collected from forms No. 2 and No. 5 of the National Statistical Monitoring in Russia and in its regions. Results and discussion. Before 2019, in some regions of Russia, CP vaccination of children within regional immunization programs and vaccination of risk groups within the vaccination schedule following the epidemic-response measures had hardly any effect on the epidemiological situation. The remote-work and stay-at-home policies during the COVID-19 pandemic in 2020 resulted in a decrease in the incidence and an increased number of individuals who did not have immunity against Varicella zoster, thus subsequently leading to the increased CP incidence in the country. However, the Central, Volga, and Siberian Federal Districts were able to avoid an increase in the CP incidence due to the significantly increased vaccination coverage among children in 20202021. At the same time, in most of the regions, less than 2% of children aged 16 years were vaccinated annually. The insufficient CP vaccination coverage in the regions having extensive experience of planned immunization of children led to the shift of the incidence towards older age groups and increased risk of development of congenital infection. Conclusion. To increase the effectiveness of CP preventive vaccination, it is recommended that the national vaccination schedule should include two-dose vaccination with the coverage of at least 90% of one-year-old children, while continuing immunization of older age individuals from the groups that are at risk of infection.