Evaluation of Humoral immunity in military persons vaccinated against meningococcal meningitis type A and C in Iran

This research was performed to determine the level of the humoral immunity in military persons vaccinated against meningococcal meningitis type A and C in IRAN. Each person was given a subcutaneous injection of 50µg of group A and C polysaccharides vaccine. blood samples were collected from 150 combatants before vaccination as well as at 1,4,7 month after vaccination. Antibody level in the sera was measured by passive hemaglutination. A titer 16 (1-2 µg/ml) in the serum was considered as protective. 3.3% of persons had a protective level of antibody in the circulating before vaccination. One month after vaccination, 89% of persons had protective level of antibody in their sera. The circulating antibody level in only 7.4% of vaccinated did not rise to a protective level. About 3.3% vaccinated did not produce specific antibody at all. The antibody level in vaccinated persons four month after vaccination not only did not rise but also it showed a decrease in circulating antibody level, but the number of combatants with protective levels of antibody did not decrease. The antibody levels in vaccinated combatants seven month after vaccination continued to fall, and in 18% of combatants the antibody levels fell below the protective level. Regarding to a relative low level of circulating antibody after vaccination in immune combatants and a lower rate (82%) of immune individuals (as compared with the results of other investigations who report an immune rate of %90 up to 95%) as well as the continuous fall in circulating antibody after very short rise, the results of present investigation indicate that the polysaccharide vaccine which was used in this study does not provide a high rate of protective immunity. Probably, type of vaccine is important and in other researches used vaccines of another companies.