NCT04817917

Seroprevalence of Neutralizing Antibodies Against Japanese Encephalitis Virus Among 6 Years Old Children With 5 Different Immunization Strategies in Zhejiang Province

Seroprevalence of Neutralizing Antibodies Against Japanese Encephalitis Virus Among 6 Years Old Children With 5 Different Immunization Strategies in Zhejiang Province, China: An Open-labeled, Ambidirectional Cohort Study

• Status: Unknown
• Phase: Phase 4
• Study type: Interventional
• Enrollment: 712 (actual)
• Sponsor: Zhejiang Provincial Center for Disease Control and Prevention · Other Government
• Sex: All
• Age: 72 Months – 75 Months
• Healthy volunteers: Accepted

Summary

This study is to evaluate the seroprevalence of neutralizing antibodies against Japanese encephalitis (JE) virus in children aged 6 years who were previously administered with 5 different immunization strategies by JE attenuated live vaccine (JEV-L) or/and inactivated vaccine (JEV-I). The secondary objective is to evaluate the immunogenicity of the booster dose of JEV-I at 6 years old for those previously immunized with 3 doses of JEV-I or those sequential administered with 1 dose of JEV-L and another dose of JEV-I.

Detailed description

Based on the retrospective registry in Zhejiang Provincial Immunization Information System, healthy children aged 6 years from 5 cohorts were included according to their previous immunization schedules on JE: 3 doses of JEV-I (Group 1), JEV-L+ JEV-I (Group 2), JEV-L+ JEV-I + JEV-I (Group 3), JEV-I + JEV-I+ JEV-L (Group 4), and 2 doses of JEV-L (Group 5). According to immunization programs in China, a booster dose of JEV-I is needed at the age of 6 for Group 1 and Group 2. A pre-vaccination blood sample (2.5ml) will be collected to evaluate the proportions of seropositivity before the booster dose of JEV-I. A second blood sample will be collected 28-35 days after the booster dose. Immunogenicity of the booster dose will be assessed by seroconversion rates, proportions of seropositivity and GMTs for these two groups. In addition, safety will be assessed with the occurrence of adverse events reported in these two groups. For the rest three groups who have completed the immunization schedules on JE, only one blood sample will be taken at the age of 6 to evaluate the proportions of seropositivity and GMTs after 4 years post the complete immunization schedules. Plague reduction neutralization test (PRNT) against both vaccine strains (SA-14-14-2 strain for JEV-L and Beijing P3 strain for JEV-I) will be used to test neutralizing antibody titers, so as to avoid potential bias in favor of either vaccine. PRNT50 titers (the reciprocal of the serum dilution that reduced the virus plaque count by 50% compared with the virus-only controls) ≥ 1:10 are deemed as positive.

Conditions

• Japanese Encephalitis
• Vaccine Preventable Disease
• Vaccine Reaction

Interventions

Type	Name	Description
BIOLOGICAL	Japanese Encephalitis Vaccine (Vero Cell), Inactivated;	The investigators recruit 6 years old children who have been vaccinated by 2-3 doses of JE vaccines with different immunization strategies. For participants from Group 1 and Group 2 who haven't completed the JE immunization schedules, a booster dose of JEV-I will be administered at 6 years old.
OTHER	No prospective interventions	The investigators recruit 6 years old children who have been vaccinated by 2-3 doses of JE vaccines with different immunization strategies. Participants from Group 3-5 have completed the JE immunization schedules with JEV-I or/and JEV-L. No prospective intervention will be given.

Timeline

• Start date: 2021-03-01
• Primary completion: 2022-09-17
• Completion: 2023-06-30
• First posted: 2021-03-26
• Last updated: 2022-11-15

Locations

3 sites across 1 country: China