inclusion criteria: * any adult employee of the uz brussel at t1 who has been vaccinated at the uz brussel with mrna covid-19 vaccine (comirnaty®) between the 19th of january and the 5th of february 2021 after participating to phase 4 of the covemuz study (with a maximum of 5 days difference between blood drawel and vaccination) 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 mrna covid-19 vaccine (comirnaty®) between the 19th of january and the 5th of february 2021 after participating to phase 4 of the covemuz study (with a maximum of 5 days difference between blood drawel and vaccination) 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 mrna covid-19 vaccine (comirnaty®) between the 19th of january and the 5th of february 2021 after participating to phase 4 of the covemuz study (with a maximum of 5 days difference between blood drawel and vaccination) 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 mrna covid-19 vaccine (comirnaty®) between the 19th of january and the 5th of february 2021 after participating to phase 4 of the covemuz study (with a maximum of 5 days difference between blood drawel and vaccination) and has provided a signed informed consent.