[Change in serum IgG antibody during the recovery stage of Omicron variant infection in children: an analysis of 110 cases].

Objectives: To investigate the serum level of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific RBD IgG antibody (SARS-CoV-2 IgG antibody for short) in children with SARS-CoV-2 Omicron variant infection during the recovery stage, as well as the protective effect of SARS-CoV-2 vaccination against Omicron infection.
Methods: A retrospective analysis was performed on 110 children who were diagnosed with coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 Omicron variant infection in Tianjin of China from January 8 to February 7, 2022. According to the status of vaccination before diagnosis, they were divided into a booster vaccination (3 doses) group with 2 children, a complete vaccination (2 doses) group with 90 children, an incomplete vaccination (1 dose) group with 5 children, and a non-vaccination group with 13 children. The clinical data and IgG level were compared among the 4 groups.
Results: The complete vaccination group had a significantly higher age than the non-vaccination group at diagnosis ( P <0.05), and there was a significant difference in the route of transmission between the two groups ( P <0.05). There were no significant differences among the four groups in sex, clinical classification, and re-positive rate of SARS-CoV-2 nucleic acid detection ( P >0.05). All 97 children were vaccinated with inactivated vaccine, among whom 85 children (88%) were vaccinated with BBIBP-CorV Sinopharm vaccine (Beijing Institute of Biological Products, Beijing, China). At 1 month after diagnosis, the booster vaccination group and the complete vaccination group had a significantly higher level of SARS-CoV-2 IgG antibody than the non-vaccination group ( P <0.05), and at 2 months after diagnosis, the complete vaccination group had a significantly higher level of SARS-CoV-2 IgG antibody than the non-vaccination group ( P <0.05). For the complete vaccination group, the level of SARS-CoV-2 IgG antibody at 2 months after diagnosis was significantly lower than that at 1 month after diagnosis ( P <0.05).
Conclusions: Vaccination with inactivated SARS-CoV-2 vaccine has a protective effect against Omicron infection in children. For children vaccinated with 2 doses of the vaccine who experience Omicron infection, there may be a slight reduction in the level of SARS-CoV-2 IgG antibody at 2 months after diagnosis. Citation:Chinese Journal of Contemporary Pediatrics, 2022, 24(7): 736-741 .