Date Published: January 13, 2017
Publisher: Public Library of Science
Author(s): Jan Smetana, Roman Chlibek, Irena Hanovcova, Renata Sosovickova, Libuse Smetanova, Peter Gal, Petr Dite, Daniela Flavia Hozbor.
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.
Measles is a highly contagious viral infectious disease. Measles virus (Morbillivirus) is transmitted from person to person by the airborne route. In the pre-vaccine era more than 90% of people experienced the infection during their childhood. Infants are protected by transplacentally transmitted maternal antibodies for only a few months after birth. Thereafter, all individuals are susceptible to the infection. Natural measles infection results in life-long immunity. Another option to induce a long-term protection is vaccination.
Over the past decade, except for 2014, only isolated cases of measles have been reported in the Czech Republic. Such epidemiological situation can be connected with high vaccination coverage against measles, which in the Czech Republic, over the long term, exceeds 95% . Nationwide mandatory vaccination in the Czech Republic was introduced in 1969 in a one-dose schedule, which was changed to a two-dose schedule in 1975. Individuals vaccinated with one dose of the vaccine could have been revaccinated within the vaccination campaigns provided for 6–15 years old children . In other European countries vaccination against measles was implemented into the NIP during a similar timeframe. Given the unstable epidemiological situation of measles in Europe, we are faced with a question of the persistence of the protection in adulthood after vaccination during childhood.
Our results confirm the long-term persistence of high seropositivity rate after natural measles infection. By contrast, seropositivity after vaccination decreases over time. Similarly, the concentrations of specific antibodies in persons with history of measles persist for a longer time period and at a higher level than in vaccinated persons. It shows that natural infection provides better protection than vaccination. Our study indicate possible gap in measles protection in adults born after implementation of vaccination into the NIP. Achieved results should start a discussion about real level of measles susceptibility in adults in the Czech Republic, particularly in persons born during 1970–1980. Because of persistence of immunity, measles might therefore become a disease that can occur more often even in countries with high levels of vaccination coverage, such as the Czech Republic, not only in unvaccinated children, but especially in the adult population.