Should the Second Dose of Measles Vaccine be Performed at an Earlier Age?

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Measles is a highly contagious disease which is a significant cause of mortality and morbidity worldwide. The time between epidemics increased as vaccinations increased and the age for having the disease increased, whereas measles epidemics used to occur every 2-3 years in the prevaccination era. Although there is a reliable and effective vaccination program against measles, children who do not get the vaccine, or who cannot form sufficient level of antibodies with a single vaccine dose, remain susceptible to measles, which, in turn,causes the measles virus to be pandemic. Sensitivity to measles in school-age children is high, and school epidemics have an important role in measles outbreaks. The age at which the administration of measles vaccine is performed is determined according to the age at which children lose maternal antibodies transferred from their mothers. This critical agevaries from society to society. Due to the low rate of vaccination in under developed or developing countries, the antibodies passing from the mother disappear early, and routine measles vaccination is madeat 6 or 9 months of age. Due to the higher vaccination rate in developed countries, the antibodies passing from the mother disappear later, and routine measles vaccination is performed at 12 or 15 months of age. However, in both situationsa second dose of vaccine is necessary. The American Advisory Committee on Immunization Practice [ACIP] and the American Academy of Pediatrics [AAP] declare that 4-6 years of age is the ideal time for the second dose of vaccine, and in most countries a second dose of measles, mumps, and rubella [MMR] vaccine is given at this age.

The significant decrease in mortality and morbidity provided by vaccinations confirms the success and significance of immunization programs. Preventive antibody levels can be measured serologically with various intervals after primary vaccination in order to establish appropriate immunization programs. Due to immigration from neighboring southern countries, an increase in measles cases has recently been identified in Turkey. As measles cases have appearedin children of 4–6 years of age who have not had their second dose of vaccine, it has been suggested that the second measles vaccination be given at the age of 4 years instead of 6-7 years when children are in the first year of primary school. However, to our knowledge, there is no comparative study investigating the effectiveness of vaccinations at this age based on the serologic measurement of preventive antibody levels. In this study our aim, thus, was to measure the measles antibody levels of children who have not yet had the second dose of measles vaccine at 4 to 6 years of age. We have also evaluated the necessity of a second dose of measles vaccine at 4 years of age instead of 6 years of age in a period when the risk for measles is increasing.

Linked Immunosorbent Assay (ELISA) method, and a measles specific kit was used for this method. According to the suggestions of the kit manufacturer, values of ≤10 IU/mL were accepted as non-protective. Statistical analysis of the data was performed using IBM SPSS Statistics 18.0 software. Definitive statistical and Mann-Whitney U tests were used for the evaluation of the mean value of intragroup antibody levels and analysis of anthropometric measurements and demographic data. A probability value less than 0.05 (p<0.05) was accepted as statistically significant.