Evaluating the longitudinal effectiveness of preventive measures against COVID-19 and seroprevalence of IgG antibodies to SARS-CoV-2 in cancer outpatients and healthcare workers

Summary Background It has been assumed that cancer patients, especially those undergoing chemotherapy, are at increased risk for infection and severe illness from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) compared to the general population. After the first alert message from the local healthcare service, a series of drastic measures were taken at our outpatient clinic to contain the spread of coronavirus disease 2019 (COVID-19). Methods In this retrospective study, all consecutive cancer outpatients completed a baseline SARS-CoV‑2 test via real-time polymerase chain reaction (RT-PCR) from 15 March to 26 May 2020. In the later phase, after the peak of the pandemic, patients as well as healthcare workers were tested for anti-SARS-CoV‑2 IgG antibodies. Results Between 15 March and 26 May 2020, 0.78% ( N = 5/640) cancer patients tested positive for SARS-CoV‑2 by RT-PCR. Between 22 June and 17 July 2020, anti-SARS-CoV‑2 IgG antibodies were detected in 2 out of 250 (0.8%) cancer patients and 2 out of 36 (5.5%) healthcare workers. In only 1 out of 4 cancer patients with confirmed COVID-19 infection, could SARS-CoV‑2 antibodies be detected. Conclusion Our findings suggest that the majority of our patients and healthcare workers had not been infected with SARS-CoV‑2 and rapidly implemented measures were effective. Maintenance of preventive measures should be continued until vaccines or specific treatments are available.