Duration of SARS-CoV-2 shedding: A systematic review

Background Positive viral severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) cultures indicate shedding of infectious virus and corresponding transmission risk of coronavirus disease 2019 (COVID-19). The research question of this systematic review was: Is there a discernible pattern in the timing of SARS-CoV-2 virus isolation, and what is the proportion of positive and negative results for isolation of SARS-CoV-2 virus with viral culture relative to the onset of clinical symptoms or the day of diagnosis, as indicated by longitudinal studies? Methods We systematically searched PubMed and Embase from inception to 16 February 2023 for English-language studies with serial viral culture testing within symptomatic or asymptomatic SARS-CoV-2 infected persons during the post-vaccination period. Outcomes of interest were the daily culture status per study and the overall daily culture positivity rate of SARS-CoV-2. We critically appraised the selected studies using the Newcastle-Ottawa quality assessment scale. Results We included 14 viral shedding studies in this systematic review. Positive viral SARS-CoV-2 cultures were detected in samples ranging from 4 days before to 18 days after symptom onset. The daily culture SARS-CoV-2 positivity rate since symptom onset or diagnosis showed a steep decline between day 5 and 9, starting with a peak ranging from 44% to 50% on days -1 to 5, decreasing to 28% on day 7 and 11% on day 9, and finally ranging between 0% and 8% on days 10-17. Conclusions Viral shedding peaked within 5 days since symptom onset or diagnosis and the culture positivity rate rapidly declined hereafter. This systematic review provides an overview of current evidence on the daily SARS-CoV-2 culture positivity rates during the post-vaccination period. These findings could be used to estimate the effectiveness of public health control measures, including treatment and preventive strategies, to reduce the spread of COVID-19.