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Published on: December 10, 2013
Immunity to Streptococcus pyogenes and Common Respiratory Viruses at Age 0 to 4 Years After COVID-19 Restrictions
Kitt Dokal1, Samuel Channon-Wells1,2,3, Catherine Davis4
1Department of Infectious Disease, Imperial College London, London, United Kingdom.
Insights
Nonpharmaceutical interventions (NPIs) during COVID-19 reduced immunity to Streptococcus pyogenes and RSV in young children. This may explain the recent surge in invasive S pyogenes disease.
Area of Science:
- Pediatric infectious diseases
- Immunology
- Epidemiology
Background:
- An unexplained increase in invasive Streptococcus pyogenes (group A Strep) infections occurred in European children from 2022-2023.
- Nonpharmaceutical interventions (NPIs) implemented during the COVID-19 pandemic altered the circulation of respiratory pathogens.
Purpose of the Study:
- To investigate if changes in respiratory pathogen circulation due to NPIs affected children's immunity to S pyogenes and common respiratory viruses.
- To explore a potential link between NPIs, altered pathogen exposure, and the rise in invasive S pyogenes infections.
Main Methods:
- A cross-sectional study involving children (0-4 years) with suspected infections and healthy controls across 10 European countries.
- Collected throat swabs for pathogen detection and measured serum IgG antibody levels against S pyogenes, RSV, influenza, common cold coronaviruses, and SARS-CoV-2.
- Compared data from before (Sept 2016-Mar 2020) and after (Apr 2020-Jul 2023) NPI implementation.
Main Results:
- Detection of S pyogenes, RSV, common cold coronaviruses, and influenza decreased during the peak NPI period (Mar 2020-Jul 2021).
- Children aged 3-4 years recruited after NPIs showed significantly lower IgG antibodies to S pyogenes and RSV compared to those recruited before.
- This antibody reduction was equivalent to approximately a one-year delay in immunity acquisition.
Conclusions:
- The introduction of NPIs was associated with reduced circulation of key respiratory pathogens.
- A significant decrease in serum antibodies to S pyogenes and RSV was observed in 3-4 year old children post-NPIs.
- These findings suggest a potential immunological basis for the increased incidence of invasive S pyogenes infections in this age group.
Importance:
The upsurge in invasive disease caused by Streptococcus pyogenes among children reported in several European countries during 2022 to 2023 has not been fully explained.
Objective:
To evaluate whether changes in the circulation of common respiratory pathogens associated with the introduction of nonpharmaceutical interventions (NPIs) during the COVID-19 pandemic were associated with acquisition of immunity to S pyogenes and common respiratory viruses.
Design, Setting, And Participants:
This cross-sectional study recruited children with suspected infection and afebrile control participants at hospitals in 10 European countries. Data were collected before (September 2016 to March 2020) and after (April 2020 to July 2023) the introduction of NPIs.
Main Outcomes And Measures:
Molecular detection of bacterial and viral pathogens on throat swabs and age-stratified total serum immunoglobin G (IgG) reactivity to S pyogenes cell wall extract from 2 strains, respiratory syncytial virus (RSV), 5 influenza viruses, 4 common cold coronaviruses, and SARS-CoV-2, measured by immunoassay.
Results:
Throat swabs from 1942 children aged 0 to 4 years were tested for respiratory pathogens (1449 recruited before introduction of NPIs [median (IQR) age, 19.7 (8.2-38.1) months; 798 (55.1%) male]; 493 recruited after [median (IQR) age, 20.7 (9.7-38.1) months; 269 (54.7%) male]). A decrease in detection of S pyogenes, RSV, common cold coronaviruses, and influenza viruses was observed between March 2020 to July 2021, corresponding to the maximal period of NPIs. Antibodies to S pyogenes were measured in 252 children recruited before NPIs and 200 thereafter. Antibodies to viral antigens were measured in 230 children before NPIs and 92 thereafter. Total IgG to S pyogenes and RSV was significantly lower in children aged 3 to 4 years recruited after NPI introduction compared with those recruited before (S pyogenes emm1 strain: after, 67 participants; median [IQR] 0.13 [0.44-0.44] relative units [RU]; before, 87 participants; median [IQR] 0.35 [0.10-0.65] RU; P = .007. RSV: after, 30 participants; median [IQR] 49.6 [31.1-120.7] mesoscale units [MU]/1000; before, 76 participants; median [IQR] 141.8 [78.1-423.1] MU/1000; P < .001). No such differences were observed for children aged 0 to 2 years or for individual influenza viruses or SARS-CoV-2.
Conclusions And Relevance:
In this cross-sectional study, there was a significant reduction in serum antibodies to S pyogenes and RSV in children aged 3 to 4 years after introduction of NPIs. Equivalent to approximately a 1-year delay in acquisition of immunity, these data suggest a putative biological basis for the 2022 to 2023 upsurge in severe S pyogenes infections in this age group.
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