[Analysis of measles immunity level and serological susceptibility among Yunnan residents aged ≥20 years].

Objective: To evaluate the population immunity to measles and explore the factors associated with measles susceptibility in Yunnan residents aged ≥20 years. Methods: 2 689 residents aged ≥20 years were selected by multistage stratified systematic randomized sampling in 252 villages of 42 counties in Yunnan Province between June and September in 2015. Each subject was surveyed by the same questionnaire, including general information, measles contained vaccine history, measles history, and 5 ml blood sample of each subject was collected. Serum IgG antibodies against measles virus were measured by ELISA. Positive was defined as the antibody concentration ≥250 mU/ml, and negative as <250 mU/ml. Non-conditional logistic regression model was used analyze the factors associated with measles susceptibility in adults. Results: Among 2 689 subjects, 1 214 were males (45.15%), and the overall positive rate of measles IgG antibody was 89.77%. Compared with subjects from the region where economic development was low, subjects from the region where economic development was moderate were likely to be susceptible to measles virus ( OR= 1.81, 95 %CI: 1.33-2.47). Four age groups had higher risk of being susceptible to measles virus (compared with ≥40 years: 20-24 years old, OR= 2.04, 95 %CI: 1.26-3.31; 25-29 years old, OR= 3.72, 95 %CI: 2.37-5.86; 30-34 years old, OR= 1.94, 95 %CI: 1.22-3.09; 35-39 years old, OR= 1.81, 95 %CI: 1.07-3.05). Conclusion: Our results suggest that the serological susceptibility in adults (20-39 years), especially adults from the regions where the economic development was moderate, should be concerned. The additional vaccination strategy targeting young adults is important for reducing the risk of measles infection.