Background Hepatitis B virus (HBV) is a public health threat with a global strategic goal to achieve total elimination and end the epidemic by 2030. The monitoring of HBV surface antigen (HBsAg) and HBV surface antibody (HBsAb) was carried out in Yunnan Province from 2016 to 2020, and Dali Prefecture participated in this work as the investigation site.

Objective To investigate the status of HBV infection and the associated factors of HBsAb positive rate in Dali.

Methods Stratified cluster sampling was used to conduct questionnaire survey and serum collection in 18 904 people of 6 age groups in Dali Prefecture from 2016 to 2020. enzyme linked immunosorbent assay was applied. Serum HBsAg, HBsAb and HBV core antibody (HBcAb) were detected by ELISA. Generalized Linear Mixed Models (GLMM) were used to analyze the factors associated with HBV infection rate and positive rate of HBsAb.

Results The standard HBV infection rate was 33.88%, the Hepatitis B vaccine (HepB) vaccination rate was 24.42%, the timely vaccination rate was 16.37%, and the full vaccination rate was 23.90%. The positive rates of standardized HBsAg, HBsAb and HBcAb were 2.32%, 39.95% and 18.57%, respectively. GLMM analysis showed a lower risk of infection in men than in women (OR: 0.889, 95% CI: 0.811-0.974) . Compared with the 0-1 year age group, the infection rate was highest in the ≥60 year age group (OR: 9.223, 95% CI: 5.440-15.636). The infection rate of the timely vaccinated group and the whole vaccinated group was lower than that of the non-timely vaccinated group and the incomplete vaccinated group, and the OR values were 0.670(95% CI:0.514-0.875) and 0.072(95% CI:0.055-0.094), respectively. The positive rate of HBsAb in males was higher than that in females(OR: 0.922, 95% CI: 0.862-0.987). Compared with 0-1 year old group, HBsAb positive rate in 12-18 years old group was the lowest(OR:0.032, 95% CI:0.026-0.040), and HBsAb positive rate in the whole vaccination group was higher than that in the whole vaccination group(OR:1.1614, 95% CI: 1.391-1.872).

Conclusion The positive rate of HBsAg in Dali is lower than the epidemic level, and the positive rate of HBsAb in adolescents and adults is lower. Basic immunization and reseeding should be done to improve the immunity level of the whole population.