Capturing the complete clinical spectrum and incidence of severe acute Group A Streptococcus (GAS) disease: a population-based study in Auckland, New Zealand

Abstract

Background: The global health burden of Streptococcus pyogenes (Group A Streptococcus, GAS) disease has led the World Health Organization to declare GAS vaccine development an international priority. Severe acute GAS disease comprises hospitalised infections, toxin-mediated disease (scarlet fever and streptococcal toxic shock syndrome) and immune-mediated disease (acute rheumatic fever [ARF] and acute post-streptococcal glomerulonephritis). This study aimed to characterize the burden and spectrum of severe acute GAS disease in Auckland, New Zealand, to inform future GAS vaccine studies in this setting. Methods: This prospective population-based multicentre cross-sectional observational study utilized laboratory data and ARF notifications to capture all hospitalised GAS infections and toxin- and immune-mediated disease cases associated with hospitalisation in Auckland during 2023. The epidemiology, clinical features, incidence and hospitalisation costs of these cases are described. Findings: The complete clinical spectrum of severe acute GAS disease was observed, with 606 cases captured corresponding to 1:2000 people affected each year (52 cases/100,000 population/year). The burden is inequitably distributed across the population, greatest at the intersection of age, ethnicity and socioeconomic deprivation. In the most deprived areas, approximately 1:400 Pacific children <10-years and 1:200 Pacific adults ≥80-years are affected annually (261 and 483 cases/100,000 population/year, respectively). Direct hospitalisation costs exceeded $13·2 million New Zealand dollars. Interpretation: This study demonstrates that the complete clinical spectrum of severe acute GAS disease occurs in Auckland and is associated with a substantial health and economic burden. The high incidence and entire range of severe acute GAS disease present make Auckland an ideal location for future vaccine studies. Funding: Ministry of Health New Zealand, Health Research Council of New Zealand (HRC-NZ), Royal College of Pathologists of Australasia (RCPA) Foundation.