Clinical characteristics and IgG antibody response against SARS-CoV-2 among COVID-19 patients in the POYUN factory (Hai Duong) outbreak, 2021

We conducted a cross - sectional study, from Jan 2021 to May 2021, on COVID-19 cases of the POYUN factory outbreak in Hai Duong province, to describe clinical features and explore IgG antibodies against SARS-CoV-2 status. Data from COVID-19 patients were extracted from the National Notifiable Infectious Disease Information System, and 137 blood samples were collected for ELISA testing; statistical analyses were conducted using STATA version 16.0. Among 182 COVID-19 patients, females accounted for 73.6%, the mean age was 30.2 ± 6.1. Approximately 40% of patients had onset symptom(s); the incubation period was 7.6 (95%CI: 6.5 - 8.7) days. Clinical symptoms included fatigue (36.3%), cough (34.6%), sore throat (32.4%), and fever (31.3%); other symptoms such as muscle/joint pain, and chill,… ranged from 24% - 30%. Nearly 65% of blood samples were IgG-positive; higher IgG (+) proportions were seen among patients with onset symptoms (77.4%), fever (82.4%), chill (85.7%), muscle/joint pain (84.8%), and loss of taste/smell (96.1%). The median time of IgG antibody response was 50 days post-infection, and 65.5% of patients who contracted COVID-19 ≥ 45 days had IgG (+) in their blood samples. COVID-19 patients presented with fever, muscle/joint pain, cough, and loss of taste/smell were more likely to be IgG positive. The limitations of our research included small sample size, using the convenient sampling method, and using one cut point for ELISA testing… which may lead to potential bias. In conclusion, patients in the POYUN outbreak showed specific symptoms of SARS-CoV-2 infection. The IgG antibody response among COVID-19 patients was not prolonged and was associated with presented symptoms.