ABSTRACT
@#Abstract: Objective To investigate whether the complement system of COVID-19 is affected by vaccination, and also to explore the relationship between complement and length of stay in hospital, with a view to providing input for clinical diagnosis and the management of COVID-19 patients. Methods The patients admitted from November 1st to November 30th, 2021 in the Eighth Affiliated Hospital of Guangzhou Medical University were selected as subjects. According to the time of vaccination, the patients were divided into two groups as vaccinated within half a year and over half a year. Then C3, C4, IgG, IgM, IgA, COVID-19 IgG and IgM, neutral granulocyte and lymphocyte count were detected and all patients' hospitalized days were recorded. With their hospitalization days of 14 d as a threshold, the patients were divided into two groups, and the above indicators were compared. Results C3 concentration was (0.86±0.157) g/L in patients with vaccination within six months, which is significantly lower than (0.96±0.172) g/L in those over six months (P<0.05), but as for C4, IgG, IgM, IgA, COVID-19 IgG and IgM, neutral granulocyte and lymphocyte counts, there were no significant difference between two groups; as for the patients within 14 days of hospitalization, C3 and C4 concentrations were lower than those for more than 14 days, but the COVID-19 antibody IgG and IgM, lymphocyte counts were higher (all P<0.05). Conclusion Vaccination within half a year can make the body's immune function and complement system to identify viruses earlier, more beneficial to remove viruses, but this effect is weakened after half a year; when admission, C3, C4, COVID-19 IgG level and lymphocyte counts can be used to predict hospitalization time in COVID-19 patients.