Systematic differences were identified for symptoms of Omicron infected individuals between early and late stage of the COVID-19 pandemic in China

AimWe aimed to investigate the differences in clinical features (specifically, patterns of symptoms) of the COVID-19 patients in the early and late stage of this large scale COVID-19 outbreak in Shaanxi Province in China based on data from a large scale survey. MethodsThis study used baseline data from a large survey to investigate the characteristics of the COVID-19 pandemic in Shaanxi province from Dec.2022 to Jan. 2021. A total of 44 sampling clusters (11 villages in rural areas and 33 residential urban areas) were chosen for enrollment of study participants. A self-developed questionnaire was applied to data collection. A total of 14,744 individuals were included, and data from 12,111 valid participants were collected for further analysis. The Patients infected before Dec. 15th 2022 were classified as early stage infects patients while those infected after Jan. 1st 2023 as late stage infects patients. ResultsInformation of 2,854 COVID-19 patients, comprising of 1,710 (16.7%) patients infected during the early stage and 1,144 (11.2%) during the late stage, were extracted from the background survey. Most of the COVID-19 typical symptoms (11 out of 12) were found to be more frequent in COVID-19 patients infected during the early stage compared to those infected during late stage. Nine of them showed statistical significance including fever ({chi}2=93.42, P<0.001), cough ({chi}2=8.97, P=0.003), muscle or body pain ({chi}2=17.57, P<0.001), headache ({chi}2=8.28, P=0.004), sore throat ({chi}2=10.10, P=0.002), nausea or vomiting ({chi}2=8.40, P=0.004), loss of taste or smell ({chi}2=45.05, P<0.001) and chills ({chi}2=8.17, P=0.004). The significance of most of these symptoms were kept after being adjusted for multiple variables. ConclusionIndividuals infected with the Omicron variant at an earlier stage of a COVID-19 outbreak are more prone to developing certain symptoms compared to those infected at late stage.