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Objectives
We compared the viral cycle threshold (Ct) value of infected patients to better understand the viral kinetics during the dominant period in which a specific virus type according to the vaccination status in Gyeonggi Province, Republic of Korea.
Methods
We obtained case-specific data from the COVID-19 surveillance system, Gyeonggi in-depth epidemiologic report system, and Health Insurance Review & Assessment (HIRA) Service from January 2020 to January 2022. We defined the dominant periods according to the viral sequencing test result and explored Ct values. Using a generalized additive model, we performed a nonlinear regression analysis to determine viral kinetics over time.
Results
Cases in the delta variant dominant period had higher viral shedding patterns than cases in other periods. The temporal change of virus shedding did not differ according to the vaccination status in the omicron variant dominant period but decreased in patients who completed the third vaccination in the delta variant dominant period. The time from symptom onset to peak viral shedding based on the E gene in the case of the omicron and delta variant dominant periods was approximately 2.4 days (95% CI: 2.2-2.5) and 2.1 days (95% CI: 95% CI: 2.0-2.1), respectively.
Conclusions
In the one-time tests conducted to diagnose SARS-CoV-2 infection in a large population, although individual characteristics were not adjusted, it was confirmed that the viral shedding differed according to the dominant strain and vaccination history. These analysis results give utilization value for hundreds of thousands of test data produced at SARS-CoV-2 screening test centers.