EVALUATION OF THE EFFECTIVENESS OF PREEXPOSURE RABIES VACCINATION IN IRAN

Background – Rabies is a zoonotic viral disease which infects mammals. It is transmitted to humans and other animals by an infected animal bite. Once the symptoms of the disease develop, rabies is fatal. Rabies is found in all provinces and cities of Iran especially in northern regions, from North-West to North-East of the country. The main objective of this study was to determine the level of antirabies antibody titer in preexposure-vaccinated high-risk individuals working in antirabies treatment centers in Iran and to compare them with WHO standards. Methods – In this study, the serum antibody titers of 2,490 vaccinated high-risk staff working in antirabies treatment centers were surveyed to determine the level of antirabies antibody titers. The titers were then compared with WHO standards. From June, 1999 through June, 2000, rabies antibody titers were measured by ELISA in WHO Collaborating Center for Reference and Research on Rabies, Pasteur Institute of Iran. Antibody titers were classified in 3 groups: 1) below 0.5 IU/mL, 2) 0.5 – 10 IU/mL, and 3) above 10 IU/mL. Results – The antibody titer in the group having received complete vaccination with booster was significantly higher than the group with incomplete vaccination (p < 0.5). The level of antibody titer decreased with time. Our results indicated that this period was about two years for the titers above 10 IU/mL and 5 years for the titers between 0.5 and 10 IU/mL. Conclusion – A booster dose should be injected within a maximum of 2 years which is very important in raising antirabies antibody titer. We concluded that the interval between the last vaccine injection and the time of sampling inversely correlates to the antibody titer.