Humoral Immunity against Measles in Mother–Infant Pairs during the First Year of Life in Greece: A Cross-Sectional Study

Measles outbreaks have surfaced in Europe during the last decades. Infants <12 months of age were the most severely affected pediatric population. The aim of this study was to investigate the duration of maternally derived measles antibodies in infants aged 1 to 12 months in relation to maternal humoral immune status and other parameters. In a prospective, cross-sectional cohort study, 124 mother/infant pairs and 63 additional infants were recruited from October 2015 through December 2019. Infants were hospitalized in a university pediatric department of a general hospital. Demographic and epidemiological data were recorded and blood samples were collected from mothers and their infants. Commercially available enzyme-linked immunosorbent assay (ELISA) was used for measuring measles antibodies. Fifty nine percent of mothers had vaccine-induced and 15% infection-acquired measles immunity. Eighty-eight percent and 94% of infants were unprotected by 5 and 10 months of age, respectively. Maternal antibody levels and infant age were significant independent predictors of infants’ antibody levels whereas the method of maternal immunity acquisition, age, and origin [Greek/non-Greek] were not. Our findings suggest that about 90% of infants are susceptible to measles beyond the age of 4 months. To our knowledge, these are the first data from Greece reported under the current community composition and epidemiological conditions.

Characteristics of measles immunity in students of the pediatric faculty of a medical university

Objective: to evaluate the intensity of measles immunity in students of I–VI courses of the pediatric faculty of St. Petersburg State Medical University.Materials and methods: titers of antibodies to measles virus were determined in 986 students of I–VI courses in May –June 2019. The level of measles antibodies was determined by enzyme-linked immunosorbent assay.Results: positive (protective) titres of measles antibodies were detected in 555 people. (56.4%), the absence of measles immunity was found in 431 people. (43.6%), including 57 people. (5.8%) specific antibodies were not detected. The relationship between the level of collective immunity and the duration of the period after the last vaccination against measles was revealed.Conclusions: in the majority of examined students (96.2%), protective titers of measles antibodies remained for 10 years after the last vaccination. Subsequently, a significant decrease in the level of measles antibodies was noted. All students who do not have a protective IgG titer are shown measles vaccination with live measles vaccine in accordance with the instructions for use.

Seroprevalence of measles antibodies and factors associated with susceptibility: a national survey in Mexico using a plaque reduction neutralization test

Measles continues to be one of the leading causes of child mortality worldwide, even though a highly effective vaccine has existed for more than 40 years. We aimed to describe the seroprevalence of measles antibodies in Mexico in 2012 and the risk factors associated with susceptibility. A total of 7,785 serum samples were analyzed from the National Health and Nutrition Survey in Mexico. This national survey is representative of the general population, including noninstitutionalized adult, adolescent, and child populations. Antibody titers were classified into protective (> 120 mIU/mL) or susceptible (≤ 120 mIU/mL) levels. The weighted seroprevalence and susceptibility of the overall population were 99.37% (95% CI 99.07–99.58) and 0.63% (95% CI 0.42–0.93), respectively. Among 1-to-4-year-old children, 2.18% (95% CI 1.36–3.48) were susceptible to measles. Among adolescents and young adults, the prevalence of susceptibility was as follows: those 15–19 years of age had a prevalence of 0.22% (95% CI 0.09–0.57), and those 30–39 years of age had a prevalence of 1.17% (95% CI 0.47–2.85). Susceptibility was associated with young age, living in Mexico City, living in crowded households and unknown or nonvaccinated status among 1- to 5-year-old children. Although the overall sample population seroprevalence for measles is above 95%, increased susceptibility among younger children signals the importance of the timely administration of the first vaccine dose at 12 months of age. Furthermore, increased susceptibility among specific subgroups indicates the need to reinforce current vaccination policies, including the immunization of unvaccinated or incompletely vaccinated individuals from 10 to 39 years of age.

Laboratory monitoring of postvaccination measles immunity

Measles vaccination In Russian Federation was introduced in 1967. It was assumed that the twodose vaccination regime would lead to a decrease in the incidence and elimination of measles. A number of studies have shown that up to 10% of individuals who received two doses of measles vaccine do not develop a specific humoral immunity, or do not maintain it at a protective level. This fact may contribute to gradual accumulation of persons susceptible for measles infection in the population, thus leading to emergence of new viral outbreaks in the future. The aim of this study was to perform dynamic monitoring of the post-vaccination measles immunity. The study involved 149 people. All the examined persons were divided into 2 groups. The group of comparison included persons, aged 19 to 51 years, in whom absence of measles immunity was serologically confirmed (n = 76). This group was twice vaccinated with live measles culture vaccine (NPO “Microgen”, Russia). Determination of IgG to measles virus was carried out 1 month after vaccination and revaccination. The control group consisted of persons with documented evidence of double immunization against measles virus, with laboratory-confirmed measles immunity (n = 73), aged 19 to 53 years. The comparative dynamics of development and contents of antibodies in the comparison-control groups were considered, with respect to the WHO age classification. Basic and postvaccinal dynamic determination of IgG to measles virus in serum was performed by ELISA using the “VectoKor-IgG” test system (Vector-Best, Novosibirsk). When analyzing the results of the study, it was noted that the level of measles immunity group in older persons from control group (over 45 years old) was initially higher, than in younger subjects. Among young people, the titers of specific measles antibodies reached the values of the control group of the corresponding age after the first vaccination, whereas the level of specific measles antibodies in older age group was significantly lower compared to the control group even after revaccination. A month after the first immunization, 4 people did not reach the protective level of anti-measles IgG. However, revaccination allowed them to form anti-measles immunity. In the course of our work, a case of non-response to vaccination was identified. Thus, our study showed a sufficient interindividual variability in humoral immune responses to measles vaccination.

Formation of humoral and cellular immunity to measles vaccine in adults

Despite adherence to the policy of mass measles vaccination in the majority of countries, this infection still remains far from being fully eradicated. Measles outbreaks are reported worldwide, when the vast majority of cases are recorded in subjects of 18—35 years of age. Studies on assessing measles IgG antibody level in different regions of Russia reveal increased percentage of measles seronegative subjects among young adults. Current study was aimed at investigating formation of humoral and cellular immunity after measles vaccination in seronegative adults aged 18 to 30 years old. There were enrolled 50 measles seronegative healthy volunteers aged 18 to 30 years old. Level of anti-measles IgM and IgG antibodies was measured by ELISA (Vector-Best, Russia). Subclasses of measles specific IgG antibodies were analyzed by ELISA, by replacing IgG conjugate for IgG1, IgG2, IgG3, IgG4 conjugates, whereas measles specific IgA antibodies were estimated by ELISA with IgA conjugate (Polygnost, Russia) at a concentration of 1 μg/ml. Antibody avidity was assessed by ELISA (Euroimmun, Germany). Cell-mediated measles immunity was estimated by CD107a surface expression on CD8hi T cell subset stimulated by measles virus-derived antigens. A specific cellular response to measles antigens before vaccination was detected in 50% of examined subjects, whereas 40% samples showed no signs of cellular immune response, with 10% of remaining cases described as equivocal. It was found that 6 weeks after vaccination all vaccinated subjects developed measles specific IgG antibodies at protective level reaching 1.33 (0.85—1.82) IU/ml [Me (LQ—UQ)]. Anti-measles IgA antibodies were of 0.655 (0.423—1.208) IU/ml [Me (LQ—UQ)]. However, no measles specific IgM antibodies were detected 6 weeks after vaccination. In addition, primary type of immune response (dominant low-avidity anti-measles antibodies IgG3 subclass) to measles vaccination was observed in 24 out of 50 subjects, whereas 26 subjects developed secondary type of immune response (high-avidity anti-measles antibodies dominated by IgG1 subclass). A measles specific cellular immune response was observed in 47 of the 50 examined subjects, and in 3 volunteers it was equivocal. Further analysis revealed a cohort of subjects who were not vaccinated against measles (18 subjects), although 60% of them provided medical record on previous dual measles vaccination occurred in childhood. Another cohort consisted of subjects who had medical record of measles vaccination in childhood (32 subjects), but lost protective measles antibodies produced by plasma cells (23 subjects), and memory T cells (3 subjects), or measles antibodies and memory B cells (6 subjects) over time. Such pattern evidences that measles-specific cellular and humoral arms immune responses were developed and maintained independently of each other.

Measles immunity in different population groups

Objective: to examine the state of the immunity to measles in different age groups.Materials and methods: In 2018, 4444 people were examined at the Diagnostic Center (virological). Among them, 3783 people were examined using the passive haemagglutination test for measles (manufactured by Pasteur Research Institute of Epidemiology and Microbiology, Russia). In the remaining 661 cases, the IgG to measles were detected using the enzyme-linked immunosorbent assay (ELISA) by VektoMeaseles IgG test (manufactured by Vector-Best, Russia). The correlation between the measles IgG level (ELISA) and the age was examined in 518 patients. Results: In this study, the immunity to measles was shown to be insufficient in all groups of observed people. Even among medical staff, nearly 10% had no protective level of measles antibodies. We have shown that the correlation between the measles IgG level and the age is statistically significant, so that the number of seronegative persons in different age groups differs significantly. Conclusion: The highest ratio of seronegative individuals was found in the age group between 18 and 25 years (52,33%), which can lead to serious measles outbreaks. Hence, this study confirms a strong need for additional immunization in all groups and especially in young population.