Long-Term Immunogenicity of Envacgen® in Children

April 28, 2026 updated by: Medigen Vaccine Biologics Corp.

Extension Study of Protocol CT-EV-31s to Examine the Long-Term Immunogenicity After Receiving Inactivated EV71 Enterovirus Vaccine (Envacgen®) in Children

This study is designed to evaluate the long-term antibody titers of Envacgen® approximately 6 years after the first vaccination dose in participants who were aged 2 months to <6 years at the time of enrollment in the CT-EV-31s study.

Study Overview

Status

Active, not recruiting

Conditions

Intervention / Treatment

Detailed Description

This is an extension study of protocol CT-EV-31s, to evaluate the long-term immunogenicity of EV71 Enterovirus Vaccine (Envacgen®).

The study will consist of a single visit approximately 6 years after the first vaccination of the EV71 vaccine or Placebo in participants aged 2 months to < 6 years when participating in the CT-EV-31s study. Immunogenicity response against EV71 virus antigen at the visit will be assessed.

Study Type

Observational

Enrollment (Actual)

220

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Taiwan
      • Hsinchu, Taiwan
        • Mackay Memorial Hospital, HsincChu
      • Taipei, Taiwan
        • National Taiwan University Hospital
      • Taipei, Taiwan
        • Mackay Memorial Hospital, Taipei
      • Taoyuan, Taiwan
        • Chang Gung Medical Hospital Linkou

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Child

Accepts Healthy Volunteers

Yes

Sampling Method

Non-Probability Sample

Study Population

Subjects who have completed participation in study CT-EV-31s.

Description

Inclusion Criteria:

  • Participants who have completed participation in study CT-EV-31s and have received protocol specified doses of EV71 vaccine or Placebo.
  • The participant and/or participant's parent/guardian is able to understand and sign the informed consent form.

Exclusion Criteria:

  • The participant and/or participant's parent/guardian refuse to comply with the study procedures.
  • After completing the CT-EV-31s trial, participants who received any EV71 vaccine before participating in this study.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
EV71 Vaccine with Adjuvant AlPO4
EV71 Vaccine Produced in Vero Cells with Adjuvant AlPO4
Biological: EV71 vaccine
EV71 vaccine with Adjuvant AlPO4 and the placebo (Adjuvant AlPO4 only) were randomly administrated to subject in CT-EV-31s study
Adjuvant AlPO4
Placebo (Adjuvant AlPO4 only)
Biological: EV71 vaccine
EV71 vaccine with Adjuvant AlPO4 and the placebo (Adjuvant AlPO4 only) were randomly administrated to subject in CT-EV-31s study

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Serum neutralizing antibody titer
Time Frame: Approximately 6 years after first dose of vaccination.
Geometric mean titer (GMT) of EV71 neutralizing antibody at approximately 6 years after first dose of EV71 vaccination or Placebo for participants.
Approximately 6 years after first dose of vaccination.
Seroprotection rate
Time Frame: Approximately 6 years after first dose of vaccination
Seroprotection rate (defined as neutralizing antibody titer ≥1:32) at approximately 6 years after first dose of EV71 vaccination or Placebo for participants.
Approximately 6 years after first dose of vaccination

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Medigen Vaccine Biologics Corp.

Investigators

  • Principal Investigator: Cheng-Hsun Chiu, M.D., Ph.D., Chang Gang Memorial Hospital, LinKou
  • Principal Investigator: Chien-Yu Lin, M.D., Ph.D., Mackay Memorial Hospital, HsinChu
  • Principal Investigator: Nan-Chang Chiu, M.D., Mackay Memorial Hospital
  • Principal Investigator: Li-Min Huang, M.D., Ph.D., National Taiwan University Hospital

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

November 24, 2025

Primary Completion (Actual)

February 16, 2026

Study Completion (Estimated)

July 31, 2026

Study Registration Dates

First Submitted

April 28, 2026

First Submitted That Met QC Criteria

April 28, 2026

First Posted (Actual)

May 5, 2026

Study Record Updates

Last Update Posted (Actual)

May 5, 2026

Last Update Submitted That Met QC Criteria

April 28, 2026

Last Verified

April 1, 2026

More Information

Terms related to this study

Keywords

Other Study ID Numbers

  • FU-EV-31

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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