Immunogenicity after booster dose with mRNA BNT162b2 among elderly or adult with underlying diseases who had received AZD1222 using standard versus low dose via intramuscular route (COVID-19)

Status

Active, not recruiting

Phases

Phase 2

Study type

Interventional

Source

TCTR

Registry ID

TCTR20211027002

Enrollment

200

Registered

2021-10-27

Start date

2021-11-24

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

Prevention of COVID-19 with booster SARS-CoV-2 vaccine using BNT162b2, comparing standard dose vs low dose, in elderly or adult with underlying diseases. SARS-CoV-2, mRNA vaccine, ChAdOx1 nCoV-19 vaccine, Immunogenicity, Reactogenicity

Interventions

BNT162b2 30 ug ,BNT162b2 15 ug

Active Comparator Biological/Vaccine,Experimental Biological/Vaccine

BNT162b2 (standard dose),BNT162b2 (low dose)

Eligibility

Sex/Gender

All

Age

18 Years to 69 Years

Inclusion criteria

Inclusion criteria: 1. Participants must age 18 to 69 years old on the day of vaccination and meet either cohort inclusion criteria. o Cohort 1: Participants must age 60 to 69 years old on the day of vaccination. o Cohort 2: Participants must have underlying disease e.g., diabetes mellitus, chronic kidney disease, cardiovascular disease. o Cohort 3: Participants must be considered immunocompromised e.g., currently taking immunosuppressant, active cancer currently on treatment. o Cohort 4 (Control): Participants must age 18 to 59 years old and be in good health at the time of entry into the trial as determined by medical history, physical examination (including vital signs), and the clinical judgment of the investigator. 2. Participants must have received 2 doses of AZD1222 vaccination with interval at least 8 weeks apart. 3. Participants must have received 2nd dose of AZD1222 for more than 60 days at the day of vaccination. 4. Participants must be able to communicate effectively with study personnel and considered reliable, willing, and cooperative in terms of compliance with the protocol requirements. 5. Participants must sign a written informed consent form, including any required privacy authorization form, prior to the initiation of any trial procedures, after the nature of the trial has been explained according to local regulatory requirements.

Exclusion criteria

Exclusion criteria: 1. Known anaphylaxis to any of the trial vaccine components (including excipients of the trial vaccines) or drugs. 2. Participants with previous documented SARS-CoV-2 infection within 6 months of vaccination day by history obtained from participant(s) and/or positive anti-nucleocapsid test(s). 3. Receipt of immunoglobulins or blood products within 3 months on the day of vaccination. 4. Receipt of any other vaccines within 14 days (for inactivated vaccines) or 28 days (for live vaccines) prior to enrollment in this trial.

Design outcomes

Primary

Measure	Time frame
Surrogate virus neutralization test (sVNT) to variants of concern e.g. Delta strain Day 0, day 14, day 90 ELISA	—

Secondary

Measure	Time frame
Anti-S-RBD IgG Day 0, day 14, day 90 BIOTEC COVID-19 IgG ELISA,T cell response Day 0, day 14, day 90 ELISpot,Safety Day 14, day 90 Solicited local and systemic adverse events, Unsolicited adverse events	—

Countries

Thailand

Contacts

Public ContactProf. Thanyawee Puthanakit

Department of Pediatrics, Faculty of Medicine, Chulalongkorn University

thanyawee.p@chula.ac.th6622564930

Outcome results

None listed

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