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


Back-ground: In developing countries, measles is regarded as a serious problem and can only be combated by large-scale vaccination programs. The main known risk factor for primary vaccine failure is age at vaccination, due to persistence of maternal antibodies, which interferes with the success of measles immunization. Objectives: Identification of sero-prevalence rate of inherited measles IgG- antibodies among infants aged 9-12months, before measles vaccination. And assessment of acquired sero-conversion rate after inoculation of measles vaccine among those infants. Subjects and Methods: A cross –sectional study, was conducted in a selected primary health care centers in 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/2007 to the 31st January/2008. Anti measles IgG antibodies (Abs), were detected in the serum by Enzyme Linked Immuno-Sorbent Assay, using “Dade Behring” standard test kit. Results: The results revealed that the mean & geometric mean measles IgG Abs titers, before measles vaccination were negative (cut off= <330 mIU/ml). After measles vaccination, the mean changed to a positive value (cut off= >330mIU/ml- <1909mIU/ml), but geometric mean titer remained in a negative level. Inherited measles IgG Abs in the serum samples of those infants was 9.4%, before measles vaccination, while sero-convertion rate was 70.3%, acquired after measles vaccination. Conclusion: The least of infants were sero-positive at 9th months (before measles vaccination age) , and a positive sero-conversion obtained after that vaccine, with a primary vaccine failure in about quarter of them.