In the wake of the unprecedented COVID-19 pandemic, the global healthcare sector has witnessed the profound and ongoing impact of the viral infection on various aspects of public health. One crucial area of concern pertains to the potential influence of the pandemic on the incidence and distribution of invasive respiratory infections caused by Streptococcus pneumoniae, Hemophilus influenzae and Neisseria meningitidis – three highly invasive bacterial species that colonise the oropharynx/nasopharynx when transmitted via respiratory droplets.1,2,3 Among these species, S. pneumoniae and H. influenzae have been identified as the most potentially ‘fatal’ bacterial species, given their antibiotic resistance.4
The Invasive Respiratory Infection Surveillance (IRIS) Consortium, encompassing 30 countries and territories across five continents, was established in early 2020; their primary objective was to investigate the incidence and geographical distribution of the invasive bacterial infections caused by S. pneumoniae, H. influenzae and N. meningitidis during the first two years of the COVID-19 pandemic (2020–21), versus the pre-pandemic years (2018–19).1,5 To study the aforementioned bacterial pathogens, Streptococcus agalactiae, an invasive pathogen that spreads via a non-respiratory route, was used as a comparator to evaluate the stability of routine disease surveillance during the pandemic.1 The IRIS Consortium submitted surveillance data gathered from January 1 2018 to January 2 2022 to specialized databases within ‘Public databases for molecular typing and microbial genome diversity’ (PubMLST).1 In order to quantify the effect of COVID-19 restrictions on the four invasive pathogens studied, Shaw and colleagues employed time-series modelling methods to assess changes in bacterial disease epidemiology during the first two years of the pandemic, ultimately estimating the quantity of prevented cases.1 The Consortium utilised data such as patient age and bacterial serotype to evaluate shifts in epidemiological patterns that could impact future disease prevalence and vaccination strategies.1
Key findings of the study included1:
Overall, findings from this comprehensive analysis unveiled critical insights regarding the complex relationship between the COVID-19 pandemic and invasive respiratory infections. The sustained decline in invasive diseases observed may be attributed to the global enforcement of COVID-19 containment strategies designed to curtail the spread of SARS-CoV-2 infections, which simultaneously reduced the transmission of other respiratory infections.1 The substantial number of averted cases (~36,000) is understood to have alleviated the burden on health-care systems amid the pandemic.1
Nevertheless, such altered patterns of microbial transmission and disruptions in routine global immunisation schedules have raised concerns of decreased population immunity, or ‘immunity-debt’ (a higher proportion of susceptible individuals within a population, owing to reduced exposure to commonly circulating microbes) that could potentially lead to future disease outbreaks.1 Thereby, it is essential to proactively monitor disease patterns and rapidly address antimicrobial resistance among invasive pathogens through optimization of clinical practices and judicious use of antibiotics.