Background
Following the lifting of COVID-19 pandemic restrictions, cases of invasive group A Streptococcus (iGAS) surged in multiple countries worldwide. The reason for this increase is currently unclear. One hypothesis is that restrictions to social mixing and school attendance resulted in infrequent respiratory infections, which consequently reduced population level immunity to Streptococcus pyogenes. During the upsurge in England, in which infections due to emm1 and emm12 predominated, iGAS case incidence doubled in children and increased by ~20% in adults. Reduced systemic immunity to S. pyogenes and winter viruses has been identified in children. Here, we set out to understand if adult immunity to S. pyogenes was also affected by the COVID-19 pandemic.
Aims & Methods
We analysed serum from healthy females using antenatal booking samples collected in Dec, Jan, Feb, (100 samples/month) of each year from 2018-2022. To provide a measure of overall immunity to S. pyogenes, we established an ELISA to measure IgG titres to emm1 S. pyogenes cell wall extract (CWE). A 6-plex Luminex assay, to determine responses to individual S. pyogenes antigens, and a superantigen neutralisation assay were also employed.
Results & Conclusions
There were no significant differences in anti-S. pyogenes CWE serum IgG titres pre- versus post-pandemic. Since CWE contains components that are common across many Gram-positive bacteria, we hypothesise that this response may not be wholly S. pyogenes specific. However, these preliminary findings demonstrate a difference between adults and children, suggesting a greater impact of non-pharmaceutical interventions on children’s immunity compared with adults.