Queensland COVID-19 Vaccination (QoVAX) Safety and Efficacy Trial Program: Mixed Dose 1 and 2 Study

Metro North Hospital and Health Service

Dataset description

The primary outcome measure is serum IgG spike concentration at 4-6 month post vaccine Dose 2, and 4 weeks after the COVID-19 booster dose. The comparison of interest is heterologous compared to homologous vaccine groups.
Data will be analysed using a General Linear Model with log-normal distribution to compare (log) fold-increase in serum IgG.
Treatment group, vaccine type given at Dose 1 and 2, and age will be used as covariates to adjust for potential confounding given ATAGI has recommended the AZ vaccine for older and Pfizer for younger individuals.
Values below the limit of detection (LoD) of the test will be replaced by values equal to the LoD divided by two. No replacement of missing data will be considered for the primary outcome. Univariate analysis will be used to explore the relationships between IgG and host intrinsic and extrinsic factors, pre-existing health conditions, medications and vulnerable groups.
Additional exploratory descriptive analysis including IgG to SARS-CoV-2 nucleocapsid, HLA-type, gender, immunocompetence and ethnicity as covariates are planned.
Secondary outcomes include for a subset of patients: neutralizing antibody titres, serum and salivary IgA levels, and cell mediated immunity to original vaccine strain. Descriptive comparative analysis between Groups 1 and 2 and other targeted subgroups for the primary outcomes will also be undertaken. Medium-term health analysis of participants will be evaluated by integration of result test results with vaccine notification data to investigate vaccine efficacy outcomes in relation to immune response and data on other health and social determinants.
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Source Study

Trial acronym


Trial ID



Not available


Not Applicable


Government body,Queensland Health

Scientific enquiries

Prof Janet Davies

Brief Summary

The overarching primary research question for the QoVax SET Mixed Dose 1 and 2 study is; In the Queensland community, do heterologous COVID-19 vaccine doses 1 and 2 compared with homologous doses 1 and 2, offer higher recall levels of spike IgG, spike IgA, neutralizing IgG, and cell mediated immunity at 4 months post dose 2. The QoVAX Mixed Dose 1 and 2 study will address these specific research questions; 1. What are the host intrinsic (HLA type, genetic traits, immunological T and B cell recep ....
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Key Inclusion Criteria

People in Queensland 18 years of age and older, who have received two doses of BNT162b2 or ChAdOx1 COVID vaccines, the second of which was received between 120-180 days prior to giving consent,

Key Exclusion Criteria

1. Unable or decline to give informed consent 2. Have a contraindication to venepuncture 3. Insufficient literacy to read and understand the English or translated version of the participant information and consent forms who do not have a family member or interpreter to assist 4. Do not posses a smart phone or computer to access the participant information and complete the consent form and fill the questionnaire. 5. Are unable or unwilling to reach a pathology collection centre to donate samples.

Can healthy volunteers participate?




Sample Size    586

Min. age    18 Years

Max. age    No limit

Sex    Both males and females

Condition category    COVID-19 , SARS-CoV-2

Condition code    Infection , Inflammatory and Immune System , Respiratory


Intervention code Not applicable

Heterologous COVID-19 vaccines (BNT162b2 (BioNTech, Pfizer)/ChAdOx1 (Oxford, AstraZeneca) or ChAdOx1/BNT162b2) for doses 1 and 2 Participants complete a questionnaire and have blood and saliva samples collected at 4 - 6 months post the second vaccine dose. The questionnaire and samples are repeated at 4 weeks after the COVID-19 booster dose, and 12-months post the date of recruitment.


Control group Active

Homologous COVID-19 vaccines BNT162b2/BNT162b2 (BioNTech, Pfizer) or ChAdOx1/ChAdOx1 (Oxford, AstraZeneca) for doses 1 and 2 Participants complete a questionnaire and have blood and saliva samples collected at 4 - 6 months post the second vaccine dose. The questionnaire and samples are repeated at 4 weeks after the COVID-19 booster dose, and at 12-months post the date of recruitment.


Outcome: Serum IgG antibodies titres to the SARS-CoV2 spike protein measured using Abbott Core Laboratories' chemiluminescent microparticle immunoassay (CMIA)
Timepoint: 4 - 6 months from the second dose of vaccine and repeated at 4 weeks after the COVID-19 booster dose, and at 12 months following the date of recruitment.

Study Protocol: Not Available
Data Dictionary: Not Available

Will individual participant data (IPD) for this trial be available?


What data in particular will be shared?

De-identified participant data and biological samples for which the participant has consented to the future use of their data and samples.

When will data be available?

Immediately following publication and no end date.

Available to whom?

Researchers undertaking projects specific to COVID-19.

Available for what types of analyses?

Analyses for specific COVID-19 related research approved by a Human Research Ethics Committee.

Source study information is derived from the Australian New Zealand Clinical Trials Registry (ANZCTR). For more information on the ANZCTR, please see