The aims of the study were to examine age-related features of immune response to measles virus in staff of a large city hospital and to define groups at risk for measles outbreaks.Methods. The study involved 1,855 staff members of a large city hospital aged ≥ 19 years old who had documented vaccination against measles or a history of measles. The participants were divided into age groups with 5-year intervals starting from 19 years of age; there were 11 groups in total. The immune response to measles virus was measured in sera by ELISA using Vector-Best IgG-Kor test system (Russia).Results. Young employers of 19 to 23 years of age were most susceptible to measles; protective antibody level was not detected in 38.5% of them. They were followed by young-to-middle-aged workers (24 to 48 years old) who were negative for anti-measles antibodies or had non-protective level of antibodies in 16.7% to 27.5%. The anti-measles antibody level was low (42.3 % to 60.0 %) in employers of 19 to 43 years of age and gradually increased to 46.3% – 92.2% in the group of 44 to 68 years old.Conclusion. Herd immunity against measles in employers of a large city hospital did not meet requirements for successful infection control which implicates ≤ 7% of seronegative individuals. This means that measles outbreak could occur at any time because the proportion of seronegative individuals (11.5%) twice exceeded the cut-off value; the antibody level was controversial in 3.2% of individuals. Therefore, monitoring anti-measles antibody level in hospital staff is necessary to detect groups at risk who should be vaccinated against measles.

It has been proven that post-vaccination immunity to measles virus after two doses of vaccine is not able to persistently protect against infection throughout life. The goal of this research was to determine the immune layer to the measles virus among women in labor and maternity ward personnel in the same medical institution. The levels of IgG antibodies to measles virus in the umbilical cord blood of 594 women in labor and 88 workers of the maternity ward were studied by ELISA. It was revealed that 22.7% of umbilical cord blood serum samples from parturient women and 21.4% of blood serum samples from maternity ward personnel were seronegative (<0.18 IU/ml). Levels of IgG antibodies to measles virus in low values (<1.0 IU/ml) were detected in 67% of blood serum samples among women in labor and 68.9% among employees of the maternity ward. Among women in labor, women under 35 years of age are at the highest risk of contracting measles; the proportion of women with low levels of protective antibodies in this age group was almost 70%, and the proportion of women without protective levels of antibodies was 23%. Compared with the age group 36–43, the age of women in labor under 35 was associated with a higher chance of not having immune protection against infection with measles virus OR [95% CI] = 2.2 [1.1–4.5] (p = 0.02) or had a low level of protection OR [95% CI] = 1.9 [1.2–3.0] (p = 0.001). It was also found that among women over 35 years of age, the proportion of persons with a high level of antibodies in women in labor was statistically significantly higher than among members of the maternity ward staff (13 and 0%, respectively, p = 0.007). Thus, maternity ward employees and women in labor constitute a risk group for measles due to the presence of a high proportion of seronegative persons among women of childbearing age (both maternity ward employees and women in labor). These conditions create the need to revise current approaches to present vaccination procedures, especially in the current epidemiological situation with COVID-19.

Within a framework of the state measles elimination program, in April, 2018 a level of measles herd immunity was assessed in 1899 Moscow hospital medical workers aged from 19 to 69 years and older. All subjects enrolled in the study were vaccinated against measles or recovered after measles infection. Serum samples were collected from subjects and examined by ELISA for measles IgG antibodies with the Vector-Best IgG-measle test system (Russia). It was found that 278 (14.6%) and 1621 (85.4%) subjects were seronegative (< 0.18 IU/mL) and seropositive (> 0.18 IU/ml), respectively. Age-related group distribution of 1855 serum samples revealed that percentage of seronegative subjects was in: aged 19—23 years was -38.5%; 24-28 and 29-33 years - 22.2%; 34-38 years - 27.5%; 39-43 years - 25.8%; 44-48 years - 16.8%; 49-53 and 54-58 years — 8.6% and 8.3%, respectively; 59-63 years old — 4.9%; 64-68 and over 69 years old — 0%. Moreover, mean level of measles IgG antibodies increased proportionally to age of medical workers from 0.58 IU/ml (19-23 years) to 2.94-2.72 IU/ml (64-68 and over 69 years). The data obtained indicate that a cohort of measles susceptible subjects (from 38.5% to 16.8%), respectively, is identified among young and middle age (from 19 to 48 years) individuals. It is assumed that two-dose measles vaccination in childhood does not contribute to the long-term preservation of protective levels of measles antibodies, thereby justifying a need to administer a three-dose measles vaccine.

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-BEST». 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.

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.