ABSTRACT
BACKGROUND: In Taiwan, the prevalence of COVID-19 was low before April 2022. The low SARS-CoV-2 seroprevalence in the population of Taiwan provides an opportunity for comparison with fewer confounding factors than other populations globally. Cycle threshold (Ct) value is an easily accessible method for modeling SARS-CoV-2 dynamics. In this study, we used clinical samples collected from hospitalized patients to explore the Ct value dynamics of the Omicron variant infection. METHODS: From Jan 2022 to May 2022, we retrospectively included hospitalized patients tested positive by nasopharyngeal SARS-CoV-2 PCR. We categorized the test-positive subjects into different groups according to age, vaccination status, and use of antiviral agents. To investigate the nonlinear relationship between symptom onset days and Ct value, a fractional polynomial model was applied to draw a regression line. RESULTS: We collected 1718 SARS-CoV-2 viral samples from 812 individuals. The Ct values of unvaccinated individuals were lower than those of vaccinated persons from Day 4 to Day 10 after symptom onset. The Ct value increased more rapidly in those individuals with antiviral drug treatment from Day 2 to Day 7. In elderly individuals, the Ct values increased slowly from Day 5 to Day 10, and the increasing trend was unique compared with that in children and adults. CONCLUSION: Our study demonstrated the primary viral infection dynamics of the Omicron variant in hospitalized patients. Vaccination significantly affected viral dynamics, and antiviral agents modified viral dynamics irrespective of vaccination status. In elderly individuals, viral clearance is slower than that in adults and children.
ABSTRACT
OBJECTIVES: The SARS-CoV-2 Omicron variant pandemic struck Taiwan in April 2022. Rapid antigen tests (RATs) play an important role in providing rapid results during a pandemic. However, self-collected samples by the children's caregivers without the supervision of medical personnel raise some concerns. METHODS: This study was performed to investigate household transmission, clinical characteristics, and antigen performance in a special COVID-19 family clinic in a children's hospital. The performance of at-home RATs was evaluated based on reverse transcription-polymerase chain reaction. RESULTS: We included 627 patients in our study between May 11 and June 10, 2022. The COVID-19 full vaccination rate was significantly higher in adults (98.5%) than in children (5.9%, P <0.001). The transmission rate was significantly higher in children (91.3%) than in adults (76.6%, P <0.001). Infected children had more incidents of fever (82.4% vs 22.4%, P <0.001) and a higher peak fever than adults. Based on the reverse transcription-polymerase chain reaction, the negative predictive rate of the home RAT was only 38.7% (95% confidence interval: 31.9-46.0%) in children. The cycle threshold value of those with false-negative antigen tests was significantly lower in children. CONCLUSION: Children had a higher transmission rate, more fever, and higher peak fever than adults. Home RAT has a suboptimal negative predictive rate in children.