Patients suffering from severe mental illness could be in increased risk for a severe outcome if infected with COVID-19. Also, there are reports on fewer treatment activities among psychiatric patients (e.g. higher heart disease mortality), lower hospitalization rate and fewer invasive cardiac procedures among persons with schizophrenia than among the general population. This conveys a risk not only for the patient but for the spread of COVID-19 in the community. At present, we expect the outcome of a COVID-19 infection to be worse among the mentioned psychiatric patient population, but whether the spread of COVID-19 differs from the pattern observed in the general population is unknown. This information is of pivotal interest to come up with sufficient treatment strategies - especially when facing a possible second surge in the COVID-19 spread. Moreover, it is to the best of our knowledge unknown whether a possible CNS COVID-19 infection will worsen existing psychopathology among patients with severe schizophrenia, schizoaffective- or bipolar affective disorder. The study is exploratory in nature including as many patients as possible for testing. The target population is patients diagnosed with schizophrenia, schizoaffective disorder or a bipolar affective disorder receiving in-patient or out-patient care via one of the psychiatric centres in The Mental Health Services in the Capital Region of Denmark. Each patient will attend 3 study visits during a period of 12 months. A blood sample for IgG and IgM analysis for will be drawn at every visit.