Effectiveness of the Oxford-AstraZeneca COVID-19 Vaccine as a 2nd Booster, the REFORCO-Brazil Study (REFORCO-B)

October 2, 2023 updated by: AstraZeneca

Real-world Effectiveness oF the OxfoRd-astrazeneca Covid-19 Vaccine as a Second bOoster Dose in Brazil (REFORCO-BRAZIL)

This study will address specific questions concerning the additional protection of the AZ COVID-19 vaccine as a second booster dose in preventing severe COVID-19 outcomes (hospitalisation, ICU admission etc) and will provide data to inform COVID-19 vaccine booster dose recommendations.

Study Overview

Detailed Description

In Brazil, second COVID-19 boosters became available to specific risk groups in early 2022. By June 2022, immunocompromised individuals aged 12 years and above, individuals aged 50 years and above, and healthcare workers were eligible for a second booster. The vaccines available for second booster doses in Brazil are produced by AstraZeneca (AZ), Janssen, Pfizer and Sinovac.

While several studies have estimated absolute vaccine effectiveness (aVE) or relative vaccine effectiveness (rVE) of second boosters of mRNA COVID-19 vaccines, only a single study has, to date, estimated aVE of AZ vaccine as a second booster dose, and no studies have estimated rVE for AZ vaccine as a second booster dose. As the pandemic progresses, more individuals are choosing to become vaccinated (and boosted) against COVID-19 and thus there is greater need to evaluate the additional protection offered by a second booster dose amongst individuals previously administered a first booster. This is particularly important in the context of waning protection of a first booster dose.

The primary objective is to estimate relative vaccine effectiveness (rVE) against COVID-19 hospitalization of the AZ COVID-19 vaccine as a second booster dose relative to a first booster dose only, of any COVID-19 vaccine, administered at least four months ago.

This study will also evaluate rVE of other vaccines used in Brazil as a second booster doses. The study will further evaluate rVE of all vaccines (including the AZ-COVID-19 vaccine) as a first booster dose relative to a complete primary series only, of any COVID-19 vaccine administered at least four months ago."

Study Type

Observational

Enrollment (Actual)

188814085

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

      • São Paulo, Brazil, 05403-010
        • Techtrials Pesquisa e Tecnologia Ltda.

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

Population A is for evaluating second booster doses and will consist of individuals aged 18 years and over with immunocompromising conditions, healthcare workers aged 18 years and over, and individuals aged 50 years and over.

Population B is for evaluating first booster doses and will consist of all individuals aged 18 and over.

Description

Inclusion Criteria:

  • Hospitalized for SARS between 01 January 2022 and 31 December 2022 (Population A) or hospitalised for SARS between 01 August 2021 and 31 December 2022 (Population B).
  • Eligible for a second COVID-19 vaccine booster dose at the time of SARS hospitalization (i.e., aged 50+ or aged 18+ and either a HCW or with an IC) for second booster objectives [Population A] OR eligible for a first COVID-19 vaccine booster dose at the time of SARS hospitalisation (i.e., aged 18+) for first booster objectives [Population B].
  • Results available for a RT-PCR and/or antigen test for SARS-CoV-2 conducted on a sample taken up to 14 days after symptom onset.
  • Individuals have required matching variables (e.g. age and sex).

Exclusion Criteria:

  • Hospitalized for COVID-19 within 3 months prior to date of current hospital admission for SARS
  • Nosocomially-acquired infection (where SARS case is flagged as nosocomial and/or where symptom onset date is after hospitalisation date)

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Observational Models: Case-Control
  • Time Perspectives: Retrospective

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Population A
For evaluating second booster doses
Used as 2nd booster, 1st booster, or primary series
Used as 2nd booster, 1st booster, or primary series.
Used as 2nd booster, 1st booster, or primary series.
Used as 2nd booster, 1st booster, or primary series.
Population B
For evaluating first booster doses
Used as 2nd booster, 1st booster, or primary series
Used as 2nd booster, 1st booster, or primary series.
Used as 2nd booster, 1st booster, or primary series.
Used as 2nd booster, 1st booster, or primary series.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
COVID-19 confirmed by a positive antigen test or RT-PCR test in an individual hospitalized for SARS
Time Frame: Sample date within 14 days prior to and up to 2 days after hospitalization.
Study includes SARS hospitalizations between August 2021 and December 2022 for evaluation of 1st booster dose effectiveness, and SARS hospitalizations between January 2022 and December 2022 for evaluation of 2nd booster dose effectiveness.
Sample date within 14 days prior to and up to 2 days after hospitalization.

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

July 22, 2022

Primary Completion (Actual)

May 18, 2023

Study Completion (Actual)

May 18, 2023

Study Registration Dates

First Submitted

January 23, 2023

First Submitted That Met QC Criteria

January 23, 2023

First Posted (Actual)

January 26, 2023

Study Record Updates

Last Update Posted (Actual)

October 3, 2023

Last Update Submitted That Met QC Criteria

October 2, 2023

Last Verified

June 1, 2023

More Information

Terms related to this study

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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