Comparison of Secondary Attack Rate and Viable Virus Shedding between Patients with SARS-CoV-2 Delta and Omicron Variants: A Prospective Cohort Study.

배경: There are limited data comparing the transmission rates and kinetics of viable virus shedding of the omicron variant to those of the delta variant. We compared these rates in hospitalized patients infected with delta and omicron variants. 방법: We prospectively enrolled adult patients with COVID-19 admitted to a tertiary care hospital in South Korea between September 2021 and May 2022. Secondary attack rates were calculated by epidemiologic investigation, and daily saliva samples were collected to evaluate viral shedding kinetics. Genomic and subgenomic SARS-CoV-2 RNA was measured by PCR, and virus culture was performed from daily saliva samples. 결과: A total of 88 patients with COVID-19 who agreed to daily sampling and were interviewed, were included. Of the 88 patients, 48 (59%) were infected with delta, and 34 (41%) with omicron ; a further five patients gave undetectable or inconclusive RNA PCR results and one was suspected of being co-infected with both variants. The baseline characteristics of the two groups were comparable except that fewer of the delta patients had been vaccinated, and the delta patients had more severe disease. The latter also had a higher secondary attack rate (31% [38/124]) vs. 7% [34/456], p<0.001 : Table 1). Multivariable analysis revealed that moderate-to-critical disease severity (HR 1.96), immunocompromised status (HR 2.17), fully- or 1st booster-vaccinated status (HR 0.49), and omicron infection (HR 0.44) were independently associated with prolonged viable virus shedding (Table 2). 결론: Patients with omicron infections had higher transmission rates but shorter periods of transmissible virus shedding than those with delta infections. [ABSTRACT FROM AUTHOR]