Japanese Encephalitis, Vaccine Preventable Disease, Vaccine Reaction
Conditions
Keywords
Japanese Encephalitis, Seroprevalence, Immunogenicity, Immunization schedule, Safety
Brief 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.
Interventions
BIOLOGICALJapanese 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.
OTHERNo 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.
Sponsors
Liaoning Chengda Biotechnology CO., LTD
Zhejiang Provincial Center for Disease Control and Prevention
Study design
Allocation
NON_RANDOMIZED
Intervention model
PARALLEL
Primary purpose
PREVENTION
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
72 Months to 75 Months
Healthy volunteers
Yes
Inclusion criteria
* Participants aged ≥ 72 months to \< 75 months. * Participants have completed routine immunization schedules in time. * Participants are healthy native residents. * Parents/guardians can understand the protocol requirements, provide informed consent, accept all scheduled visits, and comply with all trial procedures.
Exclusion criteria
* History of neurological diseases or related symptoms. * An acute illness with fever (temperature ≥ 37.1℃) or any acute onset of chronic diseases. * Known impairment of immunologic function, or receipt of immunosuppressive therapy or immunoglobulin in the past 3 months. * Known allergy to any constituent of the vaccine. * Have been injected with other vaccines or any clinical trial drugs in the past 4 weeks. * Any condition which, in the opinion of the investigator, would pose a health risk to the subject or interfere with the vaccine.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Proportions of seropositivity of neutralizing antibodies against JE at the age of 6 | At the age of 6. Test immediately after enrollment by a dose of blood sample. | Defined as any positive antibody (neutralizing antibody titers ≥1:10) response in children aged 6. |
| Geometric Mean Titers (GMTs) or Median antibody titers for children aged 6 years | At the age of 6. Test immediately after enrollment by a dose of blood sample. | Neutralizing antibody titers by plaque-reduction neutralization tests (PRNT). |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Seroconversion rates of the booster dose of JEV-I for Group 1 and Group 2 | before and 28-35 days after the booster dose. | Defined as any positive antibody (neutralizing antibody titers ≥1:10) response in children who were seronegative prior to the booster dose, or at least a four-fold increase for children who had pre-existing positive antibodies. |
| Proportion of seropositivity of neutralizing antibodies against JE after the booster dose for Group 1 and Group 2. | 28-35 days after the booster dose. | Defined as any positive antibody (neutralizing antibody titers ≥1:10) response after the booster dose. |
| Geometric Mean Titers (GMTs) or Median antibody titers after the booster dose for Group 1 and Group 2. | 28-35 days after the booster dose. | Neutralizing antibody titers by PRNT. |
| Safety of the booster dose for Group 1 and Group 2 | From inoculation to 30 days after the inoculation. | The occurrence of adverse events for the booster dose |
Countries
China
Outcome results
None listed