PURPOSE: According to the European Public Health Authority guidance for ending isolation in the context of COVID-19, a convalescent healthcare worker (HCW) can end their isolation at home and resume work upon clinical improvement and two negative RT-PCR tests from respiratory specimens obtained at 24-h intervals at least 8 days after the onset of symptoms However, convalescent HCWs may shed SARS-CoV-2 viral RNA for prolonged periods METHODS: 40 healthy HCWs off work because of ongoing positive RT-PCR results in combined nasopharyngeal (NP) and oropharyngeal (OP) swabs following SARS-CoV-2 infection were invited to participate in this study These HCWs had been in self-isolation because of a PCR-confirmed SARS-CoV-2 infection NP and OP swabs as well as a blood sample were collected from each participant RT-PCR and virus isolation was performed with each swab sample and serum neutralization test as well as two different ELISA tests were performed on all serum samples RESULTS: No viable virions could be detected in any of 29 nasopharyngeal and 29 oropharyngeal swabs taken from 15 long-time carriers We found SARSCoV- 2 RNA in 14/29 nasopharyngeal and 10/29 oropharyngeal swabs obtained from screening 15 HCWs with previous COVID-19 up to 55 days after symptom onset Six (40%) of the 15 initially positive HCWs converted to negative and later reverted to positive again according to their medical records All but one HCW, a healthy volunteer banned from work, showed the presence of neutralizing antibodies in concomitantly taken blood samples Late threshold cycle (Ct) values in RT-PCR [mean 37 4;median 37 3;range 30 8-41 7] and the lack of virus growth in cell culture indicate that despite the positive PCR results no infectivity remained CONCLUSION: We recommend lifting isolation if the RT-PCR Ct-value of a naso- or oropharyngeal swab sample is over 30 Positive results obtained from genes targeted with Ct-values &gt; 30 correspond to non-viable/noninfectious particles that are still detected by RT-PCR In case of Ct-values lower than 30, a blood sample from the patient should be tested for the presence of neutralizing antibodies If positive, non-infectiousness can also be assumed
An approach to lifting self-isolation for health care workers with prolonged shedding of SARS-CoV-2 RNA