Long Term Persistence and Effect of a Booster Dose of the Japanese Encephalitis Vaccine IC51

Study Overview
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Brief Summary
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The study investigates the long term persistence the Japanese encephalitis vaccine IC51 and the need of a booster dose

Detailed Description
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This is an open label, non-randomized multi-center phase 3 follow-up study. All volunteers having completed trial IC51-304 (NCT00595790) will be enrolled into this trial at 2 sites

Official Title
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Long Term Persistence and Effect of a Booster Dose of the Japanese Encephalitis Vaccine IC51

Conditions
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Japanese Encephalitis

Intervention / Treatment
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* Biological: IC51


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: At least 18 years of age Written informed consent obtained prior to study entry Subjects correctly included in and having completed study IC51-304 according to the protocol. Exclusion Criteria: Use of any other investigational or non-registered drug or vaccine in addition to the study vaccine during the study period Immunodeficiency including post-organ-transplantation or immunosuppressive therapy Pregnancy, lactation or unreliable contraception in female subjects

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: IC51<br>In study IC51-305, subjects who had received IC51 in study IC51-304 were tested for seroconversion 6 months after the first vaccination. Subjects who had protective titers were again tested for persistence of immunity at 12 months after the first immunization,whereas subjects who had titers below the seroconversion threshold by Month 6 received a booster dose of 1x6 mcg IC51 at Month 11. Their immune response was also assessed at Month 12. Thereafter, subjects who had no protective titer by Month 12 received a booster dose of 1x6 mcg IC51 at Month 23, regardless of prior treatment; and neutralizing antibody titers were reassessed at Month 24. Subjects who had protective titers at month 12 did not receive a booster at Month 23, and their neutralizing antibody titer was also assessed at Month 24. | Biological: IC51<br> <br> * Other names: Japanese Encephalitis purified inactivated vaccine;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Long Term Immunogenicity of IC51 Vaccine 24 Months After the Primary Vaccination | Seroprotection rate (SPR) (anti-JEV neutralizing antibody titer ≥ 1:10) 24 months (M24) after the primary vaccination - imputed; Persistence of immunogenicity (SPR) at M24 defined as: pos. (positive) (persistent): Subjects with a non-missing, pos. seroconversion at D56 (Study IC51-304) and without booster at M11 or M23 and with non-missing, seroprotection (SP) pos. PRNT50 at M6 or M12 and with non-missing, SP pos. PRNT50 at M24 neg. (negative) (non-persistent): Subjects with missing or neg. seroconversion at D56 (Study IC51-304) or booster at M11 or at M23, or non-missing, SP neg. PRNT50 at M6 or M12 or missing PRNT50 at both M6 and M12 or missing or SP neg. PRNT50 (serum dilution giving 50% reduction in plaques in a Plaque Reduction Neutralization Test) at M24 | - 24 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| SPR 24 Months After the Primary Vaccination (Observed) | Persistence of immunogenicity (SPR) at M24 (observed) defined as : positive (persistent): Subjects with a non-missing, positive seroconversion at D56 (Study IC51-304), and who did not receive a booster dose at Visit 2 (M11) or Visit 4 (M23), and with a non-missing, SP positive PRNT50 result at Visit 1 (M6) or Visit 3 (M12), and with a non-missing, SP positive PRNT50 result at Visit 5 (M24) negative (non-persistent): Subjects with missing or negative seroconversion at D56 (Study IC51-304), or who did receive a booster dose at Visit 2 (M11) or at Visit 4 (M23), or with a non-missing, SP negative PRNT50 result at Visit 1 (M6) or Visit 3 (M12), or with a missing PRNT50 result at both Visit 1 (M6) and Visit 3 (M12), or with a non-missing, SP negative PRNT50 result at Visit 5 (M24) | 24 months | 
| Persistent and Actual SPR 6, 12 and 24 Months After Primary Vaccination |  | - 24 months | 
| Persistent and Actual GMT 6, 12 and 24 Months After Primary Vaccination |  | 24 months | 
| SCR 1 Month After the Booster Doses |  | 1 month | 
| GMT 1month After Booster Doses |  | 1 month | 
| Safety Profile of IC51 |  | study duration |