Assessing inequalities in risk of invasive group A streptococcal infections according to residential setting, England 2015-2023

Abstract

Background: Longitudinal increases in rates of invasive group A streptococcal (iGAS) infection are being seen across high-income countries, including the UK. In the absence of a vaccine, opportunities for prevention remain limited. To identify and quantify high-risk populations, surveillance data were analysed using novel methodologies. Methods: Statutory notifications of iGAS infection from January 2015 to April 2023 in England were extracted from the UK Health Security Agency (UKHSA) national laboratory surveillance database (Second Generation Surveillance System, SGSS). Data were enhanced using address-matching methods to derive a standardised unique property reference number (UPRN) and Basic Land and Property Unit (BLPU) class denoting residential property type. Cases were traced on the NHS Spine to identify deaths. In addition, outbreaks investigated through submission of isolates to the UKHSA national reference laboratory from January 2019 to December 2023 were analysed to identify outbreak setting. Descriptive analyses were undertaken to characterise cases and outbreaks according to residential setting and identify excess risk using ONS population denominators (available for 2019-2022). Results: A total of 16,476 cases of iGAS infection were diagnosed in England between 2015-2023. Of these, all except 11 were successfully address-matched. The majority of cases were resident in a private home (n=14,865; 90.2%). 1,167 cases were resident in an institutional setting, 83.2% in care/nursing homes (n=971). Cases resident in care/nursing homes constituted 6% of all cases and 19% of cases over 75y. Whilst the number of cases in prison was low (n=44), a marked increase was noted between 2018 and 2020. Of 1,932 deaths within 7 days of diagnosis, 13% were in care home residents. Compared to over 75s in private residential settings, rates of iGAS infection in care/nursing home residents were three times higher (25.6 vs 8.4 per 100,0000 population; RR=3.05, p<0.001) and risk of death within 7d was 40% higher (19% vs 27%; p<0.001). Of 212 outbreaks/incidents investigated by the reference laboratory between 2019-2023, nearly a quarter (23%; 49) were in care/nursing homes, a similar number to outbreaks occurring in hospital settings (47; 22%). Discussion: Our study highlighted disparities in population risk of iGAS infection, particularly among residents of care homes with an estimated 1 in 4000 diagnosed with iGAS infection, over a quarter of whom died within a week of diagnosis. Conclusion: Prevention initiatives, including any future licensed vaccines should focus on the most susceptible subpopulations given the increased likelihood of infection and poor outcomes.