[Analysis of measles immunity level in persistent populations in Beijing, 2012].

Objective To analyze the measles immunity level of persistent population in Beijing.Methods A total of 2125 objects from 10 age groups,who had been living in Beijing for over 6months,were selected from urban and rural areas in Beijing in 2012.Demographic characteristics,history of measles and vaccine immunization were investigated by questionnaire.5 ml blood sample of each subject was collected,and the Measles IgG antibody was measured by ELISA assay.Results Positive rate of measles antibody was 84.71％ (1800/2125) and standardized positive rate was 88.07％.Median of antibody was 960.46 IU/L.Positive rate and median of measles antibody were significantly different between population from different age groups (x2 =341.60,P ＜ 0.01 ; H =216.27,P ＜ 0.01).Antibody positive rate and median were lowest in the ＜ 1 year age group,which were separately 43.06％ (90/209) and 185.80 IU/L;and highest in the 1-4 (97.31％ (181/186) and 2448.81 IU/L) and 5-9 years age group (96.46％(218/226) and 1910.72 IU/L).The range of antibody positive rate and median in adults of ≥ 15 years were 81.98％-90.14％ and 744.38-1474.84 IU/L Antibody positive rate and median in persistent population,which were separately 82.45％ (883/1071) and 899.82 IU/L,were lower than those in migrant population,which were 87.00％ (917/1054) and 166.19 IU/L,respectively (x2 =8.51,P ＜ 0.01 ; U =538 704.00,P ＜ 0.01).Antibody positive rate and median in population with vaccination history,which were separately 91.95％ (891/969) and 1443.11 IU/L,were higher than those population without vaccination history and people whose history unknown (32.95％ (57/173),127.33 IU/L; 86.67％ (852/983),923.73 IU/L).The difference showed statistical significance (x2 =399.92,P ＜ 0.01 ; H =202.11,P ＜0.01).Conclusion Among the persistent population in China,measles antibody level among the children aging 1-9 years old was high enough to prevent outbreak and epidemic of measles.However,we should try our best to strengthen the measles antibody level among the babies younger than 1 year old and the migrant population aging between 15 and 40 years old. Key words: Measles;  Antibodies;  Vaccines;  Immunity