[Comparison of measles incidence in different age groups with the intensity of specific humoral immunity in healthcare workers in Moscow].

INTRODUCTION: The study of the intensity of humoral immunity to the measles virus (Paramyxoviridae: Morbillivirus) (MV) remains relevant due to the ongoing registration of the cluster cases of measles (including nosocomial cases).The aim of the study was to analyze correlation between the intensity of the humoral immunity to measles virus and the measles incidence in different age groups of the Moscow residents. MATERIAL AND METHODS: A simple analytic study was carried out under the framework of measles prevention improvement program conducted in the subjects of the Russian Federation. The study included the analysis of the reasons for the increase in the proportion of seronegative individuals and the comparison of the results of seromonitoring with the data of age-related measles incidence. Throughout 2018, total 1,855 blood serum samples obtained from employees of a large hospital center in Moscow who were previously vaccinated against measles were tested for IgG antibodies (ABs) to MV. The subjects were divided into 11 groups according to their age. Statistical analysis of the obtained data was performed using nonparametric criteria. RESULTS AND DISCUSSION: The proportion of seronegative individuals among the staff of the medical facility decreased with age, from 38.5% in persons aged 19-23 to 0% among employees aged 64 and over. Persons aged 19-43 years were the most susceptible to measles infection, which was confirmed also by the highest incidence rate at these age groups (from 6.93 to 14.03 per 100,000 population). The age group most protected against measles was those over 64 years of age, who were all seropositive and had the lowest rates of incidence. This is probably due to the fact that by this age most of them have had a measles infection and have formed a sufficient immune response. At the same time, younger individuals living in the post-elimination era have only vaccine-induced ABs to MV, the level of which declines rapidly to non-protective values in the absence of boosterization due to the exposure to the wild-type strain of the pathogen. CONCLUSION: The monitoring of the MV-specific IgG- AB levels is required for employees in the medical institutions under the age of 35. Administration of the single dose of the appropriate vaccine is recommended for seronegative individuals.

[Intensity of the immunity against measles in employees of the maternity unit in Moscow].

INTRODUCTION: Measles remains an urgent problem in Russian healthcare. Despite the ongoing vaccination, there is an increase in the incidence of measles. Prevention of measles is particularly important in high-risk groups, as well as among healthcare professionals to prevent hospital-acquired outbreaks of infection. The duration of post-vaccination immunity during the elimination of measles has not been sufficiently studied, so often people who  have had measles in childhood or have 1-2 vaccinations against the disease lose their protective antibodies with age in the absence of natural boosterization.Goals and objectives. To study the intensity of specific immunity to measles in employees of the maternity unit. MATERIAL AND METHODS: The study involved 271 employees of the maternity unit aged 21 to 93 years (262 serum samples). The level of IgG antibodies (Ab) to the measles virus in the blood serum was studied by ELISA using a standard set of reagents for the quantitative determination of IgG by «VECTOR-BEST¼. The result was  considered negative if the concentration of IgG to the measles virus in tested sample was ≤ 0.18 IU/ml and  positive - if > 0.18 IU/ml. Results. The number of seronegatives ranged from 0% to 30.8% in female employees with its maximum at age of 31-35 years. The lowest proportion of seronegative and the highest proportion of seropositive women were observed among the elderly, > 60 years. DISCUSSION: There is a marked tendency for an increase of the proportion of persons with average Ab levels with age and a decrease of the proportion of persons with low Ab levels. The percentage of seronegative women among employees exceeded the recommended level, which makes it possible for an nosocomial outbreak when an infection is introduced. CONCLUSION: The authors recommend that serological testing for the intensity of the immune response against measles should be included in the standard of the pre-vaccination screening for adults.