[Evaluation of immunity persistences of different enterovirus A71 vaccine in healthy infants and young children aged 6-35 months].

Objective: To evaluate the immunity persistence of different enterovirus A71 (EV-A71) vaccines in healthy infants and young children aged 6-35 months. Methods: In this study, volunteers who were eligible in a phase Ⅳ clinical trial to receive different EV-A71 vaccines. Venous blood samples were collected from them 3 and 5 years later after receiving two doses of EV-A71 vaccines. Sero positive rate and GMT of the neutralizing antibody was calculated to evaluate the dynamic profiles of EV-A71 vaccine-induced immunogenicity. Results: A total of 169 subjects with full series of blood samples (at all the sampling points) were included in the immune persistence analysis. The positive rates of EV-A71 neutralizing antibody in four groups were all 100.00% 3 years later after full immunization, while the positive rates of neutralizing antibody in the four groups were 93.18%, 97.62%, 97.44%, and 100.00%, respectively, 5 years later after full immunization, the difference was not significant. The neutralizing antibody GMTs of EV-A71 neutralizing antibody in the study participants were 74.69 and 67.20, respectively, 3 and 5 years later after immunization, which decreased compared with that 30 days later after full immunization. There was no significant difference in neutralizing antibody GMT among the four groups 3 years later, but there was significant difference in neutralizing antibody GMT 5 years later (P<0.001). Conclusion: The immunity induced by different EV-A71 vaccines has good persistence within 5 years after full vaccination.