Trajectory and impact factors of cycle threshold values of virus load in respiratory tract in children infected with severe acute respiratory syndrome coronavirus 2 Omicron variants / 中华传染病杂志

ABSTRACT

Objective:To investigate the clinical characteristics of children infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variants, and the impact factors of duration of cycle threshold (Ct) values turning to ≥35 detected by nucleotide test.Methods:Children aged 0 to 14 years with clinical symptoms of Omicron variants infection who admitted to designated hospital in Shanghai City (Renji Hospital, South Branch, Shanghai Jiao Tong University School of Medicine) from April 7 to June 2, 2022 were enrolled. The daily nasopharyngeal swab specimens were used for SARS-CoV-2 nucleic acid detecting by polymerase chain reaction and the results were expressed as Ct values. The T Ct≥ x was defined as from the symptom onset or first positive nucleic acid test results (the earlier data) to Ct≥ x of the open reading frame 1ab ( ORF1 ab) gene, which was the time duration from the initial to a specific Ct value.Clinical data were collected, including age, sex, vaccination and comorbidities.Cox model was performed to analyzed the impact factors of T Ct≥35. Results:A total of 871 pediatric cases with a median age of two years (ranging from one month to 14 years old) were included. Among them, 474 cases (54.4%) were male, and 89 cases (10.2%) had underlying diseases including congenital heart disease, solid tumors and epilepsy. There were 572(65.7%) mild cases, 298(34.2%) common cases, one (0.1%) severe case and no critical cases or deaths. The T Ct≥35 was 12(10, 14) days. Cox model indicated that compared to children aged one to 12 months, children aged 37 to 84 months and 85 to 168 months had shorter T Ct≥35 (hazard ratio ( HR)=1.55 and 1.84, respectively, both P<0.001). After adjusted with age, comparing to unvaccinated patients, patients with one or two shots vaccine had shorter T Ct≥35 (adjected hazard ratio (a HR)=1.49, P=0.011), and common patients had longer T Ct≥35 than mild patients (a HR=0.78, P=0.002), and patients with comorbidities had longer T Ct≥35than patients without comorbidities (a HR=0.38, P<0.001).The duration of T Ct≥28, T Ct≥30, T Ct≥33 and T Ct≥35 in children without underlying diseases were 7(6, 9) d, 9(7, 10) d, 10(8, 11) d and 12(10, 14) d, respectively. Conclusions:Age, vaccination, disease severity and underlying diseases could affect the duration of SARS-CoV-2 nucleotide turning to negative (Ct value≥35) in children infected with Omicron variants.