[Analysis of the level of serum-neutralizing antibodies against Coxsackievirus A6 in a healthy population in Tianjin City from 2014 to 2020].

Objective: To investigate the level of serum-neutralizing antibodies against Coxsackievirus A6 (CVA6) in a healthy population in Tianjin City from 2014 to 2020. Methods: From March 2014 to March 2020, 5 492 healthy volunteers were recruited in Tianjin City. The demographic information, personal hygiene habits, living environment hygiene, contact history with hand, foot and mouth disease cases within 6 months before the survey, history of upper respiratory tract infection, and medical history of the subjects were investigated using a self-designed questionnaire. Venous blood was collected from the volunteers, and the level of serum anti-CVA6 IgG neutralizing antibodies was determined by the micro-neutralization assay. The level of CVA6-neutralizing antibodies was compared in different years, regions, and age groups, and the influencing factors in healthy individuals were analyzed by an ordered logistic regression model. Results: The age of 5 492 healthy volunteers ranged from 0 to 77, with M (Q₁, Q₃) of age being 21 (7, 32) years old, and a male-to-female ratio of 1∶1.09. The high, medium and low levels of CVA6-neutralizing antibodies among the volunteers were 5.39% (296), 30.35% (1 667) and 64.26% (3 529). The proportion of volunteers with high levels of CVA6-neutralizing antibodies decreased from 54.63% (437/800) in 2014 to 30.01% (229/763) in 2020, and it also decreased with age (all P values <0.001). The results of the ordered logistic regression model analysis showed that compared with those aged >35 years, volunteers aged 0-5 years had higher levels of CVA6-neutralizing antibodies [OR (95%CI): 1.39 (1.16-1.67)]. Compared with those who did not wash their hands after going out and had poor living environments, volunteers who washed their hands after going out, had good and general living environments and had lower levels of CVA6-neutralizing antibodies [OR (95%CI): 0.80 (0.70-0.91), 0.52 (028-0.88) and 0.54 (0.31-0.96), respectively]. Conclusion: The level of CVA6-neutralizing antibodies in Tianjin City remains at a relatively high level from 2014 to 2020 and shows a decreasing trend over the years.