Antibody titers and rapid antigen testing in elderly patients with SARS-CoV-2 pneumonia vs. staff of ICU and "Covid-19" wards.

The majority of patients hospitalized with COVID-19 are older individuals. Age and the comorbidities typically associated with it usually go hand in hand with a less favorable course of the disease. We were interested in the antibody response in this particular patient group as well as in the results of rapid antigen testing. In 30 elderly patients (>75 years), antibody titers (IgA and IgG) against COVID-19 were measured, and rapid antigen testing was determined about 3 weeks after the onset of symptoms of SARS-CoV-2 infection. The results were compared with those of a "high-risk" group consisting of "Covid-19" ward regular staff, as well as with "low-risk" staff consisting of members of the intensive care unit (ICU). The antibody titer against SARS-CoV-2 was determined by ELISA (EUROIMMUN™, PerkinElmer, Inc. Company); for rapid antigen testing, we used the SARS-CoV-2 Rapid Antigen test (Roche). Our investigations demonstrate a robust antibody response in the majority of elderly, comorbid patients about three weeks after the onset of infection. At this timepoint, most of the results of rapid antigen testing were negative. Furthermore, in the group of employees of our clinic ("Covid-19" ward vs. the ICU staff), the prevalence of antibodies was very low and antigen testing was negative in the whole ICU group. Although frequently comorbid, elderly patients are capable of significantly increasing antibodies against COVID-19 about 3 weeks after the onset of infection. Since the viral load can be assumed to have been low at that point, rapid antigen testing was negative in most cases. In the test group of employees of our clinic ("Covid-19" ward vs. the ICU staff), the data demonstrate that - given adequate protective measures - the risk of infection is not higher in a "Covid-19" ward compared to other wards.