Second Dose of Varicella Vaccine in Healthy Children

Immunogenicity and Safety of the Second Dose of Varicella Vaccine in Healthy Children: An Open-label Study

This study aim to assess the immunogenicity and safety of interchangeable administration of the second dose of varicella vaccine. A total of 300 healthy participants aged 15 months - 12 years will be enrolled. Written informed consent form will be obtained from participants' parents or legally acceptable representatives (and assents will be obtained from participants aged above 9 years old and written consent forms will be prepared and consent will be obtained in writing if possible from the participants aged 3-8 years old.) before enrollment. Participants will be assigned to 5 groups according to the brand of first dose varicella vaccine they received at the age of 12 months. All participants will receive the second dose of varicella vaccine manufactured by Sinovac.

The duration of individual participation from enrollment to the last onsite visit will be a maximum of 42 days. The end of study is considered the completion of the last visit for the last participant in this study.

Blood samples (2.5 - 3.0ml per time) for immunogenicity assessment will be collected. The blood samples will be collected before vaccination and 42 days after vaccination.

Study Overview

• Status: Recruiting
• Conditions: Varicella Immunisation; Varicella (Chickenpox)
• Intervention / Treatment: Biological: PROVARIX

• Study Type: Interventional
• Enrollment (Estimated): 300
• Phase: Phase 3

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Akdeniz, Turkey (Türkiye)
    • Recruiting
    • Akdeniz University Health, Research and Application Center (Hospital), Department of Child Health and Diseases, Department of Social Pediatrics
    • Contact: Assoc. Prof. Dr. Tuğçe TURAL KARA; Email: tugceturalkara@gmail.com
  • Ankara, Turkey (Türkiye)
    • Not yet recruiting
    • Ankara Bilkent City Hospital, Pediatrics and Pediatric Infectious Diseases Clinic
    • Contact: Prof. Betül ULUKOL; Email: betul.ulukol@gmail.com
  • Ankara, Turkey (Türkiye)
    • Recruiting
    • Hacettepe University Hospitals, Department of Pediatrics, Department of Social Pediatrics
    • Contact: Prof. Sıdıka Songül YALÇIN; Email: siyalcin@hacettepe.edu.tr
  • Ankara, Turkey (Türkiye)
    • Not yet recruiting
    • REPUBLIC of TURKEY MINISTRY of HEALTH ANKARA BILKENT CITY HOSPITAL
    • Contact: Prof. Aslı Nur Özkaya Parlakay, MD; Email: ankarash.etikkurul2@saglikgov.tr
  • Ege, Turkey (Türkiye)
    • Not yet recruiting
    • Ege University Hospital (Application and Research Center) Department of Child Health and Diseases
    • Contact: Prof. Feyza KOÇ; Email: feyzaumaykoc@yahoo.com

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

1. Healthy children aged 15 months to 12 years.
2. Have received one dose of varicella vaccine at 12 months of age in Turkey (verified by vaccination card or official electronic immunization record).
3. Written informed consent obtained from parent(s) or legally authorized representative(s); assent obtained from children as applicable according to local regulations.
4. Able to comply with study procedures, as assessed by the investigator.
5. Able to provide verifiable identification and be contacted for study follow-up during the study period.

Exclusion Criteria:

1. History of varicella-zoster virus (VZV) infection (based on parental report or medical record).
2. Known exposure to VZV within 4 weeks prior to screening.
3. Receipt of more than one dose of varicella vaccine.
4. Interval between first dose of varicella vaccine and enrollment less than 3 months.
5. Known allergy to any vaccine component or history of severe allergic reaction to any vaccine (e.g., urticaria, dyspnea, angioedema).
6. Known or suspected immunodeficiency or autoimmune disease (including but not limited to systemic lupus erythematosus, ankylosing spondylitis, autoimmune thyroid disease, asplenia, functional asplenia, or HIV infection).
7. Poorly controlled chronic disease or history of severe systemic disease.
8. Current or history of severe neurological disorders (e.g., epilepsy, convulsions or seizures excluding simple febrile seizures) or psychiatric disorders.
9. Receipt of ≥14 days of immunosuppressive or immunomodulatory therapy (e.g., prednisone ≥20 mg/day or ≥2 mg/kg/day or equivalent), or cytotoxic therapy within 180 days prior to screening, or planned use during the study period.
10. Receipt of blood products or immunoglobulins within 180 days prior to screening, or planned receipt during the study period.
11. Receipt of other investigational drugs or vaccines within 30 days prior to screening, or planned receipt during the study period.
12. Receipt of live attenuated or nucleic acid vaccines within 28 days prior to screening, or subunit or inactivated vaccines within 7 days prior to screening.
13. Fever (axillary temperature >37.2°C), abnormal vital signs, or clinically significant abnormal findings on physical examination on the day of vaccination.
14. Skin conditions at the intended injection site (e.g., inflammation, ulceration, rash, scar, or other conditions that may interfere with administration or safety assessment).
15. Acute illness or exacerbation of chronic disease within 7 days prior to vaccination, or known or suspected active infection.
16. Any condition that, in the opinion of the investigator, would make the participant unsuitable for participation in the study.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Non-Randomized
• Interventional Model: Parallel Assignment
• Masking: None (Open Label)

Number of Arms

5

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Group 1; The first dose administered was VARIVAX(varicella vaccine manufactured by Merck)	Biological: PROVARIX; Participants will receive one dose (0.5 mL) of PROVARIX (VarV), a live attenuated varicella vaccine manufactured by Sinovac (Dalian) Vaccine Technology Co., Ltd., administered as the second dose of varicella vaccination.
Experimental: Group 2; The first dose administered was VARILRIX(varicella vaccine manufactured by GSK)	Biological: PROVARIX; Participants will receive one dose (0.5 mL) of PROVARIX (VarV), a live attenuated varicella vaccine manufactured by Sinovac (Dalian) Vaccine Technology Co., Ltd., administered as the second dose of varicella vaccination.
Experimental: Group 3; The first dose administered was SUDUVAX(varicella vaccine manufactured by GC Biopharma)	Biological: PROVARIX; Participants will receive one dose (0.5 mL) of PROVARIX (VarV), a live attenuated varicella vaccine manufactured by Sinovac (Dalian) Vaccine Technology Co., Ltd., administered as the second dose of varicella vaccination.
Experimental: Group 4; The first dose administered was SKYVaricella(varicella vaccine manufactured by SK bioscience)	Biological: PROVARIX; Participants will receive one dose (0.5 mL) of PROVARIX (VarV), a live attenuated varicella vaccine manufactured by Sinovac (Dalian) Vaccine Technology Co., Ltd., administered as the second dose of varicella vaccination.
Experimental: Group 5; The first dose administered was PROVARIX(varicella vaccine manufactured by Sinovac)	Biological: PROVARIX; Participants will receive one dose (0.5 mL) of PROVARIX (VarV), a live attenuated varicella vaccine manufactured by Sinovac (Dalian) Vaccine Technology Co., Ltd., administered as the second dose of varicella vaccination.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Geometric Mean Concentration (GMC) of Varicella-Zoster Virus (VZV) Antibodies	42 days after vaccination (Day 42)
Geometric Mean Fold Rise (GMFR) of Varicella-Zoster Virus (VZV) Antibodies	42 days after vaccination (Day 42)

Secondary Outcome Measures

Outcome Measure	Time Frame
Seropositive Rate of Varicella-Zoster Virus (VZV) Antibodies	42 days after vaccination (Day 42)
Seroresponse Rate of Varicella-Zoster Virus (VZV) Antibodies	42 days after vaccination (Day 42)
Incidence of Adverse Reactions Within 42 Days After Vaccination	Day 0 to Day 42 after vaccination
Incidence of Serious Adverse Events (SAEs)	Day 0 to Day 180 after vaccination

Collaborators and Investigators

• Sponsor: Sinovac (Dalian) Vaccine Technology Co., Ltd.

Study record dates

Study Major Dates

• Study Start (Actual): January 28, 2026
• Primary Completion (Estimated): July 15, 2026
• Study Completion (Estimated): November 15, 2026

Study Registration Dates

• First Submitted: February 11, 2026
• First Submitted That Met QC Criteria: March 11, 2026
• First Posted (Actual): March 16, 2026

Study Record Updates

• Last Update Posted (Actual): March 16, 2026
• Last Update Submitted That Met QC Criteria: March 11, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Varicella Zoster Virus Infection; Infections; Virus Diseases; DNA Virus Infections; Herpesviridae Infections; Chickenpox
• Other Study ID Numbers: PRO-VZV-4010

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