The Primary Objective of This Single-center Study is to Investigate the SARS-CoV-2 Spike Glycoprotein RBD Antibody Concentration in Saliva and Serum in Healthy Non Vaccinated and Non-SARS-CoV-2 Infected, COVID-19 Convalescents, Persons Vaccinated With Pfizer-BioNTech BNT162b2, Moderna mRNA-1273 or AstraZeneca ChAdOx1 nCov-19 AZD1222 Vaccines, and Convalescent COVID-19 Patients That Have Subsequently Been Vaccinated. A Potential Difference in the Immunoglobulin Concentrations of the Pfizer-BioNTech BNT162b2 Vaccine, Moderna mRNA-1273 vaccine and the AstraZeneca ChAdOx1-S Vaccine Will be Uncovered. This Knowledge About the Mucosal Immunity Will be Important for Further Designing of Vaccine Strategies.

Inclusion Criteria:

• Written informed consent
• Both Hospital staff as well as non-health care workers will be invited to participate

Exclusion Criteria:

• Individuals not fulfilling the inclusion criteria or declining blood or saliva collection.
• Exclusion criteria are neck breathers (tracheostomy/laryngectomy patients) or other nasopharyngeal or oropharyngeal anomalies that do not allow for sampling using Salivette.

Individuals who belong to one of the following four groups will be included G1=SARS-COV-2 Naïve (=Not SARS-CoV-2 vaccinated and COVID-19 negative), G2=COVID-19 convalescents, G3=Vaccinated with Pfizer-BioNTech BNT162b2, Moderna mRNA-1273 or AstraZeneca ChAdOx1-S vaccine, G4=COVID-19 positive and vaccinated with Pfizer-BioNTech BNT162b2, Moderna mRNA-1273 or AstraZeneca ChAdOx1-S vaccine