Understanding the viral shedding time of Omicron variant BA.2 infection in Shanghai: A population-based observational study.

Objectives:To explore the multifactorial causality of prolonged viral shedding time and identify different viral shedding trajectories in Omicron BA.2 variant infections. Methods:The Kaplan-Meier method was used to estimate the survivor function, and the Cox proportional hazards model was fitted to identify factors associated with viral shedding time. Group-based trajectory model (GBTM) was used to identify different viral shedding trajectories. Ordinal logistic regression was used to identify factors that significantly impacted the trajectory membership. Results:The overall median viral shedding time was 12 days (interquartile range [IQR]: 8-15). Viral shedding time was longer for female cases, cases who were incompletely vaccinated, cases with comorbidities, cases with severe or critical infections and cases who had not taken Paxlovid within 5 days after diagnosis. Compared to the 3 to 17-year-old group, all older groups had significantly longer viral shedding times. The GBTMs based on the N gene and the ORF1ab gene were consistent. Three viral shedding trajectories were identified and age group, comorbidities, vaccination status, disease state, Paxlovid treatment were significantly associated with the trajectory membership. Conclusion:Increased age, comorbidities, incomplete vaccination, severe or critical infections, and delayed Paxlovid treatment were the risk factors for prolonged viral shedding time.