Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 15 5 2023 10 12 705 710 EN Majid Najafi-Asl Department of Parasitology, Faculty of Medicine, Hormozgan Health Institute, Hormozgan University of Medical Sciences, Bandar Abbas, Iran Soghra Abdi Department of Immunology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran Mehdi Hassani Azad Infectious and Tropical Diseases Research Center, Hormozgan Health Institute, Hormozgan University of Medical Sciences, Bandar Abbas, Iran Marzieh Norouzian Department of Laboratory Sciences, School of Allied Medical Sciences, Hormozgan University of Medical Sciences, Bandar Abbas, Iran 2023 05 11 2023 09 27 Background and Objectives: Hepatitis B is a common chronic viral infection in humans. Universal use of hepatitis B vaccine is crucial for controlling the infection, but the duration of vaccine-induced immunity remains uncertain. This study aimed to assess hepatitis B antibody levels (anti-HBs) after vaccination in infancy and adolescence, and explore the relationship between immunity levels and variables such as age, sex, BMI, place of birth, and duration since last vaccination among students at Hormozgan University of Medical Sciences from 2019 to 2021. Materials and Methods: The study included 1134 students who completed a questionnaire and provided blood samples for ELISA-based measurement of antibody titers. Results: The findings revealed that 727 students (64.1%) had no protective antibody level (anti-HBs <10 mIU/ml), 299 (26.4%) had partial immunity (anti-HBs 10-100 mIU/ml), and 108 (9.5%) had complete immunity (anti-HBs >100 mIU/ml). No statistically significant relationships were observed between anti-HBs titer and age, sex, or BMI. However, antibody titer decreased with increasing time since last vaccination (P<0.001). Conclusion: This study highlights the decline in antibody titer over time following primary vaccination. Sustained immunity against hepatitis B virus relies on antibody durability or robust immunological memory, suggesting the importance of timing booster vaccinations. https://ijm.tums.ac.ir/index.php/ijm/article/view/4227 https://ijm.tums.ac.ir/index.php/ijm/article/download/4227/1616