SWITCH ON: Analysing the Immunogenicity of Additional Booster Vaccinations in HCW

Inclusion Criteria: 1. Participant is willing and able to give written informed consent for participation in the trial. 2. Adult (male/female) between 18 and 65 years old 3. Sufficient level of the Dutch language to undertake all study requirements Exclusion Criteria: 1. Adults younger than 18 or older than 65 years. 2. Adults primed with another vaccine than Janssen, Moderna or Pfizer. 3. History of allergic reactions likely to be exacerbated by any component of study vaccines (e.g. hypersensitivity to the active substance or any of the SmPC-listed ingredients of the Janssen/Pfizer/Moderna vaccine). 4. Adults that are pregnant. 5. Currently being treated for cancer. 6. Severe kidney failure or dialyses dependent. 7. Status after organ-, stem cell- or bone marrow transplantation. 8. Use of immunosuppressant's. 9. Epilepsy. 10. HIV. 11. Bleeding disorder (e.g. factor deficiency, coagulopathy or platelet disorder), or prior history of significant bleeding of bruising following IM injections of vene puncture. 12. Continuous use of anticoagulants, such as coumarins (e.g. acenocoumarol) or novel oral anticoagulants (i.e. apixaban, dabigatran etc). 13. Participants who are currently participating in another research trial. 14. All regular contra-indications of the vaccines will be applied.