Phase 3 Clinical Trial for COVID-19 Recombinant Protein Vaccine Candidate

The phase 3 trial follows positive initial results from a phase 2 clinical trial (VAT00002)1. In that trial, the COVID-19 vaccine candidate was administered to 722 adults to assess the safety, reactogenicity and immunogenicity of 3 doses and to identify an optimal vaccine dose. Results showed strong rates of neutralizing antibody response with 95% to 100% seroconversion following a second injection in all age groups (18 to 95 years old), across all doses2.

A 10µg antigen formulation of the SARS-CoV-2 adjuvanted recombinant protein-based vaccine developed by Sanofi Pasteur in combination with GSK’s AS03 adjuvant will be evaluated in a Phase 3 trial (VAT00008)2 for efficacy, immunogenicity and safety compared to a placebo.

For more information on the phase 3 clinical trial per country,
please refer to the following contact list:

Call center number: +57 01800091133

Call center number: 1800 22 2295 (toll-free)


Call center number: 1-800-633-1610
Sanofi Trial Transparency mailbox:

Vaccines Medical Information contacts:
+254 20 5139600 / +254 733 825000/
+254 725 801128


Call center: +5073041800 / +5073829500



Our phase 3 trial

Study status: ongoing, recruitment process: ongoing

Click on the image to download the complete brochure

The trial is conducted in 2 stages, the first with a monovalent (single antigen) vaccine comprising the spike protein of the original SARS-CoV-2 virus (D614) and the second stage with bivalent (2-antigen) vaccine comprising spike protein of D614 and spike protein of the SARS-CoV-2 Beta variant (B.1.351).

Participants will be categorized as naïve (not previously infected) and non-naïve (evidence of previous infection) based on serological and virological ascertainment of prior SARS-CoV-2 infection at the time of vaccination. Non-naïve participants will be capped at 30% of the total study population.

The primary objective is the prevention of symptomatic COVID-19 with onset at least 14 days after the second injection of the vaccine in SARS-CoV-2 naïve individuals. Safety of the vaccines will be evaluated throughout the study compared to placebo. Secondary endpoints include severe COVID-19 disease and asymptomatic infection.

The entire study plans to enroll approximately >21000 participants.

Participants will be randomized equally to either the investigational study vaccine (monovalent or bivalent vaccines) or placebo.

The study will target recruitment of racial and ethnic diversity that will be representative of the countries in which the study will be conducted. The study will be 13 months long.

Eligibility criteria

Aged 18 years old or older
Able to attend all the trial visits and perform medical procedures
Participants with high-risk medical conditions or those with a previous history of COVID-19 will be eligible

Participants’ eligibility is assessed at inclusion. To participate in this new Phase 3 trial, volunteers must be 18 years old or older, willing, and able to attend all trial visits and perform medical activities. Individuals with high risk medical conditions (e.g. diabetes, hypertension, cancer…) are eligible for participation.

Individuals currently participating in another trial, or who have previously received a vaccine against COVID-19 are not eligible for this trial. At this stage of the vaccine development, women who are pregnant or breastfeeding are not yet eligible. 

How does the Trial Work?

Access to authorized/approved COVID-19 vaccine

  • Before enrolling in this study, if an authorized/approved COVID-19 vaccine is available and the participant is eligible to receive it, the study team will encourage the participant to take it. Volunteers can join the study if they have no intention of getting the authorized/approved COVID-19 vaccine at the time.
  • At any time during the study, participants are encouraged to take an authorized/approved vaccine when a vaccine becomes available to them and are encouraged to speak to the study team about their decision.
  • If one of the study vaccines is determined to be safe and effective, the protocol will be amended in consultation with National Health Authorities to a blinded cross-over study design to ensure that all participants are offered a study vaccine. 

This trial is fundamental to determine the full benefit and risks of these candidate vaccine formulations and the impact it may have to help manage and control the pandemic, reducing both the individual and public health burden of COVID-19.

The goal of this study is to generate data required for approval of each of the vaccines for use in prevention against SARS-CoV-2 infection and disease in adults. The data collected during this study will also support future development in other populations (eg, pediatrics, pregnant women).


  1. Study of Recombinant Protein Vaccines With Adjuvant as a Primary Series and as a Booster Dose against COVID-19 in Adults 10 Years of Age and Older. Available at:
  2. Sanofi and GSK COVID-19 vaccine candidate demonstrates strong immune responses across all adult age groups in Phase 2 trial, Press release, 17 May 2021. Available at :
  3. Study of Monovalent and Bivalent Recombinant Protein Vaccines Against COVID-19 in Adults 18 Years of Age and Older (VAT00008). Available at:
  4. Full protocol of Phase 3 (VAT00008):