Abstract: Objective To access the sustained immune effect in influenza A H1N1 vaccine vaccinated-blood donors as well as the level of anti-H1N1 IgG in unvaccinated-blood donors in order to provide reference for preventing and treating influenza A H1N1.Methods Anti-H1N1 IgG was detected in 1166 vaccinated-blood donors as well as 1265 unvaccinated-blood donors by ELISA method in Dongguan from January 2010 to June 2010.Results The mean positive rate and high-titer rate of anti-H1N1 IgG were 78.82% and 46.57% respectively,both of which were sustained at relatively high level after reaching their peak at vaccination time of 71-90 d.The mean positive rate of anti-H1N1 IgG in unvaccinated-blood donors was 26.01%.No difference was found in the positive rate of anti-H1N1 IgG among different gender or age groups( P >0.05).Conclusion The influenza A H1N1 vaccine,with good sustained immune effect,plays an important role in preventing and treating influenza A H1N1.The positive rate of anti-H1N1 IgG in influenza A H1N1 vaccine unvaccinated-blood donors is low.Vaccination should be strengthened.