Immunity against Measles among Vaccinated School-aged Children in Zahedan, Southeast of Iran

Background: In Iran, despite the use of vaccine since 1976, we are still having local epidemics especially in the children aged 15-20 years old. Since 1996, the yearly epidemics of measles have been reported in these groups in Sistan- Baluchestan province, south east of Iran. The present study was conducted to determinate the level of immunity in this target population in Zahedan. Methods: A total of 375 school-aged children were selected randomly from 8 schools in four areas of Zahedan city, Sistan-Baluchestan province, Iran, in 2000-1. Sera were separated in laboratory and examined for measles antibody. The titers of antibody against measles were measured using hemaglutination inhibition method. A titer of 1:4 or more was considered as positive and protective to measles. Results: A total of 298 samples (76.8%) were positive at the titer 1:4 or more. Among 375 of total cases, 349 students (93%) were vaccinated twice and 26 cases (7%) were vaccinated once. Only 78.6% of the former group was immune against measles and in the letter group, the titer of antibody was under the protective level. No significant correlation was found between seropositivity and sex (P > 0.05). Conclusion: It is concluded that the present vaccination program (at 9 and 15 months of age) for production of immunity against measles in this area is insufficient. A new vaccination program (at the age of 12 months and 4-6 years of age) can bring under control the measles by increasing level immunity.