Surveillance on immunity level in healthy population before and after an epidemic of Japanese encephalitis in Hefei city, 2007

ObjectiveTo compare the immunity level in healthy population before and after the epidemic of Japanese encephalitis in Hefei city in 2007. MethodsThe immunity level in healthy group was evaluated by cluster stratified sampling in two districts of the city as well as in two counties before and after the epidemic of Japanese encephalitis. ResultsThe overall positive rate was 61.0% (218/356) before epidemic with lower rate in countryside than that in the city. The highest rate was found for the population aged 15-19 years and the lowest rate (44.00%) was observed for the infants. The positive rate increased with age for the people younger than 20 years. After epidemic, the overall positive rate was 84.0% (296/351) with almost an equal rate being found in countryside (84.0%) and in the city (84.7%). The positive rate detected before and after epidemic was different, especially for the children younger than two years old. ConclusionThe immunity level of Japanese encephalitis in healthy population was lower before epidemic than that after epidemic, and lower in countryside than that in the city. The immunization should be strengthened in children younger than two years old, a high-risk population for suffering from Japanese encephalitis.