Diphtheria serology in adults in Central Java']Java and East Java']Java, Indonesia: the importance of continuous diphtheria vaccination

Background: Vaccination increase immunity against diphtheria, yet will decrease by aging. Therefore, boosters are needed to be done regularly. Objectives: This study aims to determine the immunity to diphtheria for the population of 16 years old and above. Methods: The sample of study were 295 collected blood serums by Riskesdas project in 2013, the criteria was above 15 years of age and originating from the Provinces of Central Java or East Java inclusively. Immunity assessment was based on antibody titer (IgG) against diphtheria using Vero Cell cytotoxicity test. Statistical analysis was performed using the X2 test. Results: The full protective IgG titer (>0.1 IU/ml) at the age of 16-20 years included 75% sample with a geometric mean titer (GMT) of 0.19 IU/ml. Yet, at the age of 21-60 years and > 60 years, full protective IgG titers only cover 45.5% and 33.3% sample with GMT respectively 0.06 IU / ml. Statistical analysis showed the relationship between age and immune status with p-value 0.003. Otherwise, no relationship between the status of immunity with sex and residency with p-values of 0.16 and 0.43. Conclusions: The immune status against diphtheria at the age of above 15 years decreases with aging.