**Table 4:** Anti-HBs titre categories of HBV immune response among the studied students after booster doses measured in mIU/ml. Z: Wilcoxon test of two related groups, MCP: P value based on Mont Carlo exact probability, ! P value based on Fisher exact probability P£: P value based on Friedman test of several related samples, 4° : Three from the 7 unprotected after the 1^{st} boosting and one from the 2 having anti-HBs level of 10-100 mIU/ml after the 1^{st} boosting, 5˜ : Four from the 7 unprotected after the 1^{st} boosting and one from the 2 having anti-HBs level of 10-100 mIU/ml after the 1^{st} boosting. |