inclusion criteria: * any adult employee of the uz brussel at t1 who has been vaccinated at the uz brussel with chadox1 ncov-19 vaccine between the 2nd of march and the 9th of march 2021 after participating to phase 4 of the covemuz study between the 25th of january and the 12th of february and has provided a signed informed consent.

inclusion criteria: * any adult employee of the uz brussel at t1 who has been vaccinated at the uz brussel with chadox1 ncov-19 vaccine between the 2nd of march and the 9th of march 2021 after participating to phase 4 of the covemuz study between the 25th of january and the 12th of february and has provided a signed informed consent.

inclusion criteria: - any adult employee of the uz brussel at t1 who has been vaccinated at the uz brussel with chadox1 ncov-19 vaccine between the 2nd of march and the 9th of march 2021 after participating to phase 4 of the covemuz study between the 25th of january and the 12th of february and has provided a signed informed consent.

inclusion criteria: - any adult employee of the uz brussel at t1 who has been vaccinated at the uz brussel with chadox1 ncov-19 vaccine between the 2nd of march and the 9th of march 2021 after participating to phase 4 of the covemuz study between the 25th of january and the 12th of february and has provided a signed informed consent.