Inherited, Versus Acquired, Measles IgG-antibodies after Measles Vaccination Among Infants in Diyala /Iraq

Abstract

Back-ground: In developing countries, measles is regarded as a serious problem and can only becombated by large-scale vaccination programs. The main known risk factor for primary vaccine failure isage at vaccination, due to persistence of maternal antibodies, which interferes with the success of measlesimmunization.Objectives: Identification of sero-prevalence rate of inherited measles IgG- antibodies among infants aged9-12months, before measles vaccination. And assessment of acquired sero-conversion rate after inoculationof measles vaccine among those infants.Subjects and Methods: A cross –sectional study, was conducted in a selected primary health care centersin Diyala Province. The study sample included 117 infants (56 males & 61 females), aged 9-12 months,selected at a random during their routine vaccination, for the period extending from the 1st of February/2007to the 31st January/2008. Anti measles IgG antibodies (Abs), were detected in the serum by Enzyme LinkedImmuno-Sorbent Assay, using “Dade Behring” standard test kit.Results: The results revealed that the mean & geometric mean measles IgG Abs titers, before measlesvaccination were negative (cut off= <330 mIU/ml). After measles vaccination, the mean changed to a positivevalue (cut off= >330mIU/ml- <1909mIU/ml), but geometric mean titer remained in a negative level. Inheritedmeasles IgG Abs in the serum samples of those infants was 9.4%, before measles vaccination, while seroconvertionrate was 70.3%, acquired after measles vaccination.Conclusion: The least of infants were sero-positive at 9th months (before measles vaccination age) , anda positive sero-conversion obtained after that vaccine, with a primary vaccine failure in about quarter ofthem.Key wards: Sero-prevalence of measles IgG. Maternal, passive measles IgG antibodies. Acquired