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We have found enough participants, so we could stop the recruitment. Thanks to all registered candidates!

Clinical trial with 3 registered COVID-19 vaccines

Who: healty adults 18-55 years of age
Start: end May 2021
Duration: 12 months, 6 visits
Reimbursement: €60 per visit

What is COVID-19

COVID-19 is an infectious disease caused by a recently discovered coronavirus SARS-CoV-2. The virus has now spread worldwide. The course of the disease is varied and can be asymptomatic or mild, but can include severe respiratory problems that can lead to hospitalisation and/or death.

Why this study?

COVID-19 is a pandemic that has a very high global death toll, puts great pressure on healthcare systems and has major socio-economic implications. Vaccines are the best way to control the pandemic and protect the population from the severe effects of COVID-19.

There are currently a number of vaccines that have been developed and approved by the competent authorities for use in Europe. The delivery of these vaccines is a delicate process and may cause delays in the vaccination campaigns. However, in order to control the pandemic, it is precisely the acceleration of vaccination campaigns that is crucial. A more flexible vaccination schedule, whereby vaccines of different brands can be administered at a lower dose or in a different schedule, could be of great benefit in speeding up vaccination campaigns.

In this study, vaccines that have already been approved for use in Europe will be administered according to a different schedule or dosage than that currently prescribed in the package leaflet.

The information on the safety and immune response of these other schedules and/or doses can provide important insights into how vaccination campaigns can be accelerated worldwide.

Course of the study

Deze studie start in mei 2021, zal 12 maanden duren en omvat 6 visites.

Visit #
Blood collection?
Visit 1
Day 0
Vaccination (short+long interval)
Blood collection (short+long interval)
Visit 2
Day 28
Vaccination (short interval only)
Blood collection (short+long interval)
Visit 3a (short interval)
Day 56
Blood collection (short interval)
Visit 3b (long interval)
Day 84
Vaccination (long interval only
Blood collection (long interval)
Visit 4
Day 112
Blood collection (short+long interval)
Visit 5
Day 182

Blood collection (short+long interval)
Visit 6
Day 364
Blood collection (short+long interval)

Study schedule

Visit 1

(2 hours)
Visit 2

(2 hours)
Visit 3a
short interval only
(45 min)
Visit 3b
long interval only
(2 hours)
Visit 4

(45 min)
Visit 5

(45 min)
Visit 6

(45 min)
26 May
23 June
20 July
18 Aug.
15 Sep.
24 Nov.
25 May 22
27 May
24 June
22 July
19 Aug.
16 Sep.
25 Nov.
26 May 22
28 May
25 June
23 July
20 Aug.
17 Sep.
26 Nov.
27 May 22
31 May
28 June
26 July
23 Aug.
20 Sep.
29 Nov. 
30 May 22
01 June
29 June
27 July
24 Aug.
21 Sep.
30 Nov.
31 May 22
02 June
30 June
28 July
25 Aug.
22 Sep.
01 Dec.
01 June 22
03 June
01 July
29 July
26 Aug.
23 Sep.
02 Dec. 
02 June 22
04 June
02 July
30 July
27 Aug.
24 Sep..
03 Dec.
03 June 22
07 June
05 July
02 Aug.
30 Aug.
27 Sep.
06 Dec.
06 June 22
08 June
06 July
03 Aug.
31 Aug.
28 Sep.
07 Dec.
07 June 22
09 June
07 July
04 Aug.
01 Sep.
29 Sep.
08 Dec.
08 June 22
10 June
08 July
05 Aug.
02 Sep.
30 Sep.
09 Dec.
09 June 22
11 June
09 July
06 Aug.
03 Sep.
01 Oct.
10 Dec.
10 June 22
14 June
12 July
09 Aug.
06 Sep.
04 Oct.
13 Dec.
13 June 22
15 June
13 July
10 Aug.
07 Sep..
05 Oct.
14 Dec.
14 June 22
16 June
14 July
11 Aug.
08 Sep..
06 Oct.
15 Dec.
15 June 22
17 June
15 July
12 Aug.
09 Sep.
07 Oct.
16 Dec.
16 June 22
18 June
16 July
13 Aug.
10 Sep.
08 Oct.
17 Dec.
17 June 22

What will happen?

During visit 1, we will check whether you fulfil all the conditions for participation in this study. There will be an interview with the doctor, a short medical examination and a blood test. Female participants will be asked to provide a urine sample for a pregnancy test.

Afterwards, you will receive

your 1st study vaccination. If you are 41 to 55 years old, you will be randomly assigned to one of 12 possible study groups. If you are 18 to 40 years old, you will be randomly assigned to one of the 7 possible study groups without Vaxzevria®, as vaccination with this vaccine is currently not recommended in Belgium in this age group.

Each group will receive a total of 2 vaccinations, with the timing of the 2nd vaccination, the brand of the second vaccination, the method of administration of the vaccines or the dose of the vaccines differing between study groups. You will not know at the start of the study which group you are assigned to.

Each vaccination will be administered into the muscle (intramuscular) of your upper arm or into the skin (intradermal) of your lower arm. After each vaccination, you will be asked to keep an electronic diary to record any side effects.

On the other visits, there will always be a short medical discussion with the study staff and, if necessary, a short medical examination. Afterwards, another blood sample will be taken to assess the immune response. On your second or third study visit, depending on the study group you are assigned to, you will receive your second vaccination.


A compensation for your travel, time and effort of €60 per visit will be transferred to you after the study. (August 2022)

Additional information

This study was approved by an independent Central Ethics Committee.

If you are interested in participating in this study, you can read further information in the information and consent form (ICF). Click here to register.

If you have any doubts about your eligibility for this study and/or have any additional questions, you can always contact us at +32-3-265-2652 or cev@uantwerpen.be