Comparison of the reactogenicity and immunogenicity of a reduced and standard booster dose of the mRNA COVID-19 vaccine in healthy adults after two doses of inactivated vaccine

Immunogenicity of the booster dose COVID-19 vaccine after complete primary series of inactivated vaccine (Sinovac) and viral vector vaccine (AstraZeneca) with full and half dose of mRNA vaccine

Status

Active, not recruiting

Phases

Phase 4

Study type

Interventional

Source

TCTR

Registry ID

TCTR20211120001

Enrollment

220

Registered

2021-11-20

Start date

2021-09-14

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 adults aged more than 18 years old COVID-19, inactivated, viral-vectored, mRNA vaccine

Interventions

This group received two dose Coronavac vaccine and boosted with 15 ug-BNT162b2.,This group received two dose Coronavac vaccine and boosted with 30 ug-BNT162b2.,This group received two dose Coronavac v

Active Comparator Biological/Vaccine,Active Comparator Biological/Vaccine,Active Comparator Biological/Vaccine,Active Comparator Biological/Vaccine

15 ug-BNT162b2,30 ug-BNT162b2,50 ug-mRNA-1273,100 ug-mRNA-1273

Eligibility

Sex/Gender

All

Age

18 Years to No maximum

Inclusion criteria

Inclusion criteria: 1. Healthy adults aged more than 18 years 2. Provide informed consent 3. Not previously infected with COVID-19

Exclusion criteria

Exclusion criteria: 1. Infected with COVID-19 2. Immunocompromised individuals

Design outcomes

Primary

Measure	Time frame
Immunogenicity day 14 and day 28 post booster anrtibody to the receptor-binding domain (RBD) of the SARS-CoV-2 spike (S) protein	—

Secondary

Measure	Time frame
neutralizing activity of sera from infected individuals day 14 and day 28 sVNT,T cell response day 14 and day 28 Quantiferon SARS-CoV-2	—

Countries

Thailand

Contacts

Public ContactYong Poovorawan

Chulalongkorn University

yong.p@chula.ac.th022564000

Outcome results

None listed

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