Comparative seroepidemiology of in children before and after the COVID-19 pandemic: a retrospective cohort study [2019-2022].

BACKGROUND

During the pandemic of the coronavirus disease 2019 (COVID-19), various public health measures effectively reduced the spread of respiratory pathogens like influenza. However, the specific effects of these measures on the transmission patterns of in children-including age and gender differences and regional transmission dynamics-remain not fully understood in Jiangsu Province. This study addressed this gap by analyzing 4 years of longitudinal serum prevalence data to measure the epidemic's impact on transmission among children.

METHODS

We retrospectively analysed the immunoglobulin M (IgM) and immunoglobulin G (IgG) detection data of in Jiangsu Children's Medical Center from January 2019 to December 2022 to study the influence of the COVID-19 pandemic on the transmission of major respiratory diseases in children in and around Nanjing. From 2019 to 2022, a total of 55,604 people took IgG tests, and 84,563 people took IgM tests. Chemiluminescence immunoassay (CLIA) was used to measure -specific IgM and IgG antibodies quantitatively. We applied one-way analysis of variance (ANOVA) for continuous variables across three or more groups, and utilized Pearson χ or Fisher's exact tests to compare categorical variables between groups.

RESULTS

From 2019 to 2021, annual testing volumes declined (IgG: 20,596 to 7,157 and 12,957; IgM: 35,910 to 9,667 and 18,107). Specifically, the IgM-positive rate for decreased from 29.6% in 2019 to 26.5% in 2020 and 22.2% in 2021. The positive rate for IgG dropped from 17.2% in 2019 to 10.0% in 2020 and 6.9% in 2021. Notably, school-age children showed significantly higher seropositivity than preschoolers (IgM: P<0.001; IgG: P<0.001), and girls had higher IgM positivity than boys (e.g., 2019: 31.8% 26.4%, P<0.001).

CONCLUSIONS

Between 2020 and 2021, COVID-19 intervention measures significantly lowered the transmission of . However, data from 2022 suggest a risk of rebound. We need to be alert the possible resurgence of in children. This calls for clinical action: increasing polymerase chain reaction (PCR) testing during the seasonal peak and focusing on monitoring school-aged children and girls.