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Pathogen-specific immunity debt in children after prolonged nonpharmaceutical interventions: a cross-sectional study
Haibo Li1, Jing LiuPhD2, Qianjiao Fang3
1National Center for Respiratory Medicine, State Key Laboratory of Respiratory Health and Multimorbidity, National Clinical Research Center for Respiratory Diseases, Institute of Respiratory Medicine, Chinese Academy of Medical Sciences, Department of Pulmonary and Critical Care Medicine, Center of Respiratory Medicine, China-Japan Friendship Hospital, Beijing, PR China; Department of Respiratory Medicine, Capital Medical University, Beijing, PR China; New Cornerstone Science Laboratory, Beijing, PR China.
Insights
Prolonged nonpharmaceutical interventions (NPIs) during COVID-19 created an immunity debt in Chinese children. Antibody levels for some respiratory pathogens declined during NPIs and rebounded afterward, indicating increased susceptibility.
Area of Science:
- Pediatric infectious diseases
- Immunology
- Epidemiology
Background:
- Nonpharmaceutical interventions (NPIs) during the COVID-19 pandemic reduced respiratory pathogen circulation.
- The impact of prolonged NPIs on childhood immunity, or "immunity debt," in China remains unclear.
Purpose of the Study:
- To investigate the serological evidence of immunity debt in young children in China following prolonged NPIs.
- To analyze pathogen-specific antibody levels against 10 common respiratory pathogens.
Main Methods:
- Cross-sectional study of 235 children (9 months-5 years) in Beijing (November 2021-October 2023).
- Measurement of serum IgG antibodies using a novel antigen-specific detection platform.
- Comparison of antibody levels across periods: during NPIs, after NPIs, and during a Mycoplasma pneumoniae epidemic; analysis of hospital nucleic acid surveillance data (2017-2023).
Main Results:
- Antibody titers against Mycoplasma pneumoniae and influenza A decreased during NPIs and rebounded post-NPIs, correlating with increased clinical detections.
- Antibody levels for influenza B, RSV, parainfluenza virus, and adenovirus remained stable.
- SARS-CoV-2 antibody titers increased after December 2022.
Conclusions:
- This study provides the first multi-pathogen serological evidence of an immunity debt in young Chinese children due to prolonged NPIs.
- The immunity debt was most significant for pathogens with high pre-pandemic prevalence or rapid antigenic drift.
- Ongoing serological surveillance and targeted vaccination are crucial for managing post-NPI epidemic rebounds.
Background:
During the COVID-19 pandemic, prolonged nonpharmaceutical interventions (NPIs) reduced the circulation of respiratory pathogens. The effects of NPIs on "immunity debt" in children are unclear, especially after almost 3 years of NPIs in China.
Methods:
Between November 2021 and October 2023, a cross-sectional study of 235 children (age 9 months-5 years) was conducted at the China-Japan Friendship Hospital, Beijing. Serum IgG antibodies against 10 respiratory pathogens, including influenza A, influenza B, respiratory syncytial virus (RSV), parainfluenza virus, adenovirus (types 7 and 55), Mycoplasma pneumoniae, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants, were measured using a novel antigen-specific detection platform. Antibody levels were compared between the following three periods: during NPIs (2021-2022), after NPIs (January-June 2023), and during the Mycoplasma pneumoniae epidemic (July-October 2023). In parallel, hospital-based nucleic acid surveillance from 2017 to 2023 was analyzed.
Findings:
IgG levels exhibited pathogen-specific patterns. Antibody titers against M. pneumoniae and influenza A declined significantly during NPIs and rebounded after the restrictions were lifted, coinciding with increased clinical detection of these two pathogens. In contrast, the antibody levels for influenza B, RSV, parainfluenza virus, and adenovirus were stable across all periods. SARS-CoV-2 antibody titers rose after December 2022, reflecting the introduction of this new pathogen.
Interpretation:
Our results provide the first multi-pathogen serological evidence that prolonged NPIs led to pathogen-specific immunity debt in young children in China. The effects were most pronounced for pathogens with high pre-pandemic circulation or rapid antigenic drift. Sustained serological surveillance and pathogen-targeted vaccination strategies can mitigate epidemic rebounds after periods of reduced exposure.
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