This single-center prospective observational study will examine immune responses to to SARS-CoV-2 and how they correlate with its virological characteristics and clinical manifestations in infected patients. Household contacts will also be included so that early immune responses and viral kinetics can be captured. Patients and contacts will be followed for 8 and 2 weeks, respectively. The study will include a maximum of 250 participants.

The primary aim of this single-center prospective observational study is to establish how immune responses to SARS-CoV-2 or to cross-reactive viruses correlate with the virological and clinical characteristics of SARS- CoV-2-infected patients and their exposed household contacts. Through iterative sampling, the viral kinetics of at least 50 infected patients will be evaluated in relation to symptom severity and innate and adaptive immune responses, while their household contacts will be observed for viral detection and immune responses. Patients and contacts will be followed for 8 and 2 weeks, respectively. The study will include a maximum of 250 participants.

Inclusion Criteria:

The following persons may be included:

• A patient of any age meeting the European Centre for Disease Control and Prevention's confirmed case definition: "A person with laboratory confirmation of virus causing COVID-19, irrespective of clinical signs and symptoms" (and/or high suspicion/actively being treated as CoVID+ cases pending test confirmation)
• Household contacts (defined as those sleeping in the same apartment/house as an infected patient) of a patient with laboratory-confirmed COVID-19 (and/or high suspicion/actively being treated as CoVID+ cases pending test confirmation), whether symptomatic or not, and whether testing positive or not during a period of 14 days

Exclusion Criterion:

• Long-term incapacity leading to the inability to provide informed consent while not having a patient representative with the ability to provide informed consent

Adults and children of all ages either infected with, or presumed to be infected with SARS-CoV-2, and their household contacts.

Fully anonymized data that are not already published may be shared on reasonable request from a qualified investigator, at the discretion of the Project Leader.