Decreasing Seroprevalence of Measles Antibodies after Vaccination - Possible Gap in Measles Protection in Adults in the Czech Republic.

In recent years, Europe has recorded an increase in the number of measles outbreaks despite the implementation of vaccination into the National Immunization Programs. The Czech Republic introduced vaccination against measles into National Immunization Program in 1969. The aim of this study was to determine seroprevalence of IgG antibodies against measles in adults.Our study was designed as a prospective, multicenter cohort study. Samples of blood were taken from adults aged 18 years and over. Specific IgG antibodies were determined by ELISA method.A number of 1911 sera samples were obtained. The total seropositivity reached 83.3%, 14.3% of the results were negative and 2.4% were borderline. When comparing the individual age groups, the highest antibody seropositivity (> 96%) was detected in persons aged 50 years and over who were naturally infected in pre-vaccine era. The lowest seropositivity was recorded in the age groups 30-39 years (61.5%), 40-49 years (77.5%) and 18-29 years (81.1%).A long term high rate of seropositivity persists after natural measles infection. By contrast, it decreases over time after vaccination. Similarly, the concentrations of antibodies in persons with measles history persist for a longer time at a higher level than in vaccinated persons. Our results indicate possible gap in measles protection in adults born after implementation of vaccination into the National Immunization Programs. There are two probable reasons, decrease of measles antibody seropositivity in time after vaccination in setting of limited natural booster and one-dose vaccination schedule used in the first years after implementation

Serological survey of mumps antibodies in adults in the Czech Republic and the need for changes to the vaccination strategy

Mumps outbreaks, especially in adolescents and young adults, have been reported in the Czech Republic. The aim of the presented study was to determine the seroprevalence of specific IgG antibodies against mumps in the adult population of the Czech Republic. The study was designed as a multicenter serological survey of adults aged 18 years and over. Specific IgG antibodies against mumps were detected in blood samples using an enzyme-linked immunosorbent assay (ELISA). A total of 1,911 serum samples were examined. The overall seropositivity reached 55.3%. In individual age groups, the highest seropositivity 63% (63.5–65.2%) was recorded in adults aged 40 years and over; the lowest seropositivity was found in adults aged 18–29 years (27.4%). The difference in seropositivity rate between the 18–29 years age group and the 40 years and over age groups was statistically significant (p < 0.001). Only the 18–29 years age group included both vaccinated and unvaccinated (born in the pre-vaccine era) individuals. In vaccinated individuals, seropositivity was reported in only 19.1% of persons; in unvaccinated individuals, seropositivity reached 48.2%. Our results demonstrate the long-term persistence of antibodies following natural infection and the decrease in seropositivity that occurs after vaccination over time. This immunity waning may account for the higher susceptibility of adolescents and young adults to mumps. Therefore, the current vaccination program in the Czech Republic could be considered as less effective. It will be modified with the shifting of the second dose of vaccine from two years of age to the preschool age

Prevalence of IgG antibodies against measles overall, by age group and by sex.

<p>Prevalence of IgG antibodies against measles overall, by age group and by sex.</p

Concentration of IgG antibodies against measles in individual age groups of vaccinated and unvaccinated seropositive persons.

<p>The line inside the box shows the median for each group, the lower and the upper edge of the box indicate 25% and 75% percentile, the distance between them (IQR—inter-quartile range) is a measure of the dispersion of values. The ends of the line segments indicate 1.5 times the IQR and values that occur outside these boundaries, are considered outliers.</p

Demographic characteristics of study subjects.

<p>Demographic characteristics of study subjects.</p

Concentration of IgG antibodies against measles in individual age groups in seropositive men and women.

<p>The line inside the box shows the median for each group, the lower and the upper edge of the box indicates 25% and 75% percentile, the distance between them (IQR—inter-quartile range) is a measure of the dispersion of values. The ends of the line segments indicate 1.5 times the IQR and values that occur outside these boundaries, are considered outliers.</p

Prevalence of IgG antibodies against measles by age group.

<p>Prevalence of IgG antibodies against measles by age group.</p

Concentration of IgG antibodies against measles in unvaccinated persons in relation to the disease history.

<p>Concentration of IgG antibodies against measles in unvaccinated persons in relation to the disease history.</p