Immunogenicity and Reactogenicity of Fractional, Heterologous Primary COVID-19 Vaccination Schedules with BNT162b2 Boosters in 5-11-year-old Thai Children: A Multicenter, Prospective, Double-blind, Randomized Control Trial

Phase 1/2 double-blinded study to Evaluate Adverse Events and Antibody level, Cell-Mediated Immune Response and Immune Response Against SAR-CoV-2 Variants after COVID-19 Vaccination in Thai Children and Adolescents

Status

Active, not recruiting

Phases

Phase 1Phase 2

Study type

Interventional

Source

TCTR

Registry ID

TCTR20220406002

Enrollment

800

Registered

2022-04-06

Start date

2022-04-04

Completion date

Unknown

Last updated

2026-08-03

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Healthy Thai Children and Adolescents Immune Response Against SAR-CoV-2 Variants, Adverse Events, COVID-19 Vaccination, Children and Adolescent

Interventions

CoronaVac/BNT162b2 (full dose),CoronaVac/BNT162b2 (half dose),BNT162b2 (full dose)/BNT162b2 (full dose),BNT162b2 (half dose)/BNT162b2 (half dose)

Experimental Biological/Vaccine,Experimental Biological/Vaccine,Experimental Biological/Vaccine,Experimental Biological/Vaccine

1,2,3,4

Eligibility

Sex/Gender

All

Age

5 Years to 16 Years

Inclusion criteria

Inclusion criteria: Males or females 5 - < 16 years of age (inclusive) Never received any COVID-19 vaccine Participant or guardian of participant understand(s) Thai language through speaking, reading and writing Participant or guardian of participant be able to communicate through electronic tools such as Google form or line. Capable of attending all study visits according to the study schedule. Capable of informed assent/consent and provision of written informed consent before any study procedures

Exclusion criteria

Exclusion criteria: Have history of severe drug or vaccine allergy (anaphylaxis)? Have ever detected COVID-19 infection? Have history of COVID-19 high risk contact? Did not receive any vaccine within 14 days before the enrollment? Have received blood transfusion, plasma, blood product, blood component, immunoglobulins, antiviral or antibodies within the last 90 days? Being pregnant? Have unstable disease or could not control the symptom? Have history of immunodeficiency or been using immunosuppressant or steroid drugs? Had any of these chronic respiratory tract disease, cardiovascular disease, chronic kidney disease, diabetes, delayed development, and severe neurological conditions? Have any unusual symptoms or medical history that considered unable to participate in the study?

Design outcomes

Primary

Measure	Time frame
Adverse events within 7 days after vaccination and upto 12 weeks after 2nd dose Proportion of adverse events	—

Secondary

Measure	Time frame
Immunological response 2 and 12 weeks after 2nd dose of vaccination RBD IgG level,Immunological response 2 weeks after 2nd dose of vaccination T cell response and NT	—

Countries

Thailand

Contacts

Public ContactOrasri Wittawatmongkol

Mahidol University

orasriw@hotmail.com0814201139

Outcome results

None listed

Source: TCTR (via WHO ICTRP) · Data processed: Aug 9, 2026