The Epidemic Process of Measles with Different Strategies of Vaccination in a Large Industrial Center of the Middle Urals

Abstract

Relevance. Measles infection still does not lose its relevance, as experts everywhere register outbreaks of the disease. The aim of the study is characterization of the measles epidemic process in the context of different strategies for its vaccination in a large industrial city to make adequate management decisions.Materials and methods. The authors used the data of statistical reports on measles incidence in Yekaterinburg in 1950–2017 as the study materials. The authors analyzed data for six periods: pre-vaccination (1950–1961), selective immunization (1962–1965), routine vaccination of children under 8 years (1966–1972), vaccination of children under 14 years (1973–1986), the introduction of mass revaccination of children (1987–2001) and the period of universal vaccination at the stage of elimination of infection (2002–2017).Results. In the pre-vaccination period, the average annual incidence rate was 1381.7 ± 162.9 per 100 ths population, the seasonal increase in the incidence was in december–may, in the structure of age groups dominated by children. During the period of selective immunization, at the stage of testing of the domestic vaccine, there was a slight decrease in the incidence to 1082.8 ± 189.1 per 100 ths population, intra-annual dynamics and age distribution of patients remained virtually unchanged. During routine vaccination of children up to 8 years of age, there was a significant reduction in the incidence to the level of 219.8 ± 110.8 per 100 ths population , which was observed in almost all age groups, with the exception of children 10–14 years and adults. Seasonal manifestations of the epidemic process were similar to previous periods. With an increase in the cohort for vaccination at the expense of children up to 14 years, there was a further decrease in the incidence to 89.9 ± 39.1 per 100 ths population, but in some years measles outbreaks were registered, with an active spread of infection among schoolchildren in educational institutions. The decision to introduce a second vaccination for 6-year olds before school made it possible to achieve a sporadic level of morbidity and to change the main parameters characterizing the epidemic process in all previous periods. The epidemic process has become intermittent. Periodic rises disappeared. When the infection was not spread, the population immunity and vaccination rates were consistent with the recommendations of who experts. However, against this background, 2016 was registered a major outbreak of measles.Conclusion. The use of different tactics of vaccination led to significant changes in the parameters of the epidemic process of measles. However, at the present stage immunization schemes do not control the situation. In this regard, it is necessary to raise the issue of introduction of revaccination against adult measles every 10 years, as well as changes in the antigenic composition of the live measles vaccine, taking into account data on circulating strains of the virus of genetic lines D and H.

Keywords

• measles
• epidemic process
• epidemiological surveillance
• vaccination strategies