Clinical characteristics of family clustering pediatric and adult cases with severe acute respiratory syndrome coronavirus 2 Omicron variant infection / 中华传染病杂志

ABSTRACT

Objective:To investigate the clinical characteristics of family clustering pediatric and adult cases with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant infection in Shanghai City.Methods:A field investigation among the pediatric cases with Omicron variant infection and their household contacts from April 4 to April 30, 2022 in Children′s Hospital of Fudan University was conducted. The informations on case finding, clinical manifestations and SARS-CoV-2 vaccination status were collected. The epidemiological and clinical characteristics were compared between pediatric cases and adult cases. The independent sample t test or chi-square test was used for statistical analysis, and the relative risk ( RR) and 95% confidence interval (95% CI) were used to evaluate the protective effect of vaccination on the infection of Omicron variant. Results:There were 1 274 family members in 297 families including 370 children and 904 adults of whom 1 110(87.13%) were infected with Omicron variant, with 989(89.10%) symptomatic and 121(10.90%) asymptomatic. There were 355 children infected with Omicron variant, of whom 337(94.93%) were symptomatic, and the main manifestations were fever (96.74%(326/337)) and cough (40.36%(136/337)). Only one pediatric case with Rett syndrome developed critically severe pneumonia. A total of 194 pediatric cases had imaging examination, 64(32.99%) showed pulmonary inflammatory lesions. There were 755 adult cases infected with Omicron variant, of whom 652(86.26%) reported symptoms, and the main manifestations were fever (73.16%(477/652)) and cough (49.85%(325/652)). Among symptomatic cases, fever was more common in pediatric cases than in adult cases, while cough was more common in adult cases than in pediatric cases, and the differences were both statistically significant ( χ2=80.87 and 8.04, respectively, both P<0.01). The fever spike was higher in pediatric cases than in adult cases ((39.3±0.7) ℃ vs (38.6±0.6) ℃), and the difference was statistically significant ( t=9.85, P<0.001). The interval from the onset of symptoms to cycle threshold (Ct) value of the nucleic acid of Omicron variant≥35 was longer in pediatric cases than in adult cases ((13.0±3.1) d vs (10.9±3.6) d), and the difference had statistically significance ( t=2.97, P=0.004). Among 160 children aged 3 to 18 years, 54 (33.75%) received two-dose vaccination. Among the 904 adults, 388 (42.92%) received two-dose vaccination and 293 (32.41%) received a booster dose. In the adult cases, the risk of symptomatic infection was reduced by only 8% ( RR=0.92, 95% CI 0.86 to 0.98, P=0.014) following two-dose vaccination, and the risks of fever and cough following booster vaccination were reduced by 42%( RR=0.58, 95% CI 0.49 to 0.67, P=0.001) and 50% ( RR=0.50, 95% CI 0.34 to 0.78, P=0.001), respectively. Conclusions:Secondary attack rate and symptomatic rate of household infection are high in the context of the Omicron variant outbreak in Shanghai. Symptomatic infection is common in children and adults in household setting. Fever is the most common symptom and fever duration is short. Booster vaccination may provide certain protection against common symptoms caused by Omicron variant infection.