In order to be eligible to participate in this study, a subject must meet all of the following criteria: 1. Work at Ziekenhuis Oost-Limburg (ZOL) or at Kinderpsychiatrisch Centrum (KPC). Students will be excluded since the long term follow-up and sampling at 1 year post-vaccination cannot be guaranteed. 2. Being vaccinated against SARS-CoV-2. Participants who did not receive the second or third dose of the vaccine (because of medical reasons or refusal of the vaccine) will not be excluded from the study, unless upon their request. Additional inclusion criteria for the optional coagulation sub study: 3. Participants vaccinated with the AstraZeneca vaccine (ChAdOx1 nCoV-19), willing to provide additional blood samples within the first 3 months (with a target at 8 weeks) after the second dose. 4. Participants presenting with a breakthrough infection, willing to provide additional blood samples at the time of the breakthrough infection. 5. Participants who received a booster vaccine, willing to provide additional blood samples within the first 3 months (with a target at 8 weeks) after the booster dose.

In order to be eligible to participate in this study, a subject must meet all of the following criteria: 1. Work at Ziekenhuis Oost-Limburg (ZOL) or at Kinderpsychiatrisch Centrum (KPC). Students will be excluded since the long term follow-up and sampling at 1 year post-vaccination cannot be guaranteed. 2. Being vaccinated against SARS-CoV-2. Participants who did not receive the second or third dose of the vaccine (because of medical reasons or refusal of the vaccine) will not be excluded from the study, unless upon their request. Additional inclusion criteria for the optional coagulation sub study: 3. Participants vaccinated with the AstraZeneca vaccine (ChAdOx1 nCoV-19), willing to provide additional blood samples within the first 3 months (with a target at 8 weeks) after the second dose. 4. Participants presenting with a breakthrough infection, willing to provide additional blood samples at the time of the breakthrough infection. 5. Participants who received a booster vaccine, willing to provide additional blood samples within the first 3 months (with a target at 8 weeks) after the booster dose.