Cohort profile: A population-based record linkage platform to address critical epidemiological evidence gaps in respiratory syncytial virus and other respiratory infections

Clinical outcomes and severity of laboratory-confirmed RSV compared with influenza, parainfluenza and human metapneumovirus in Australian children attending secondary care

INTRODUCTION

Acute lower respiratory infections (ALRIs) are a major contributor to the global infectious disease burden and a common cause of hospitalisation for children under 2 years. We compared clinical severity in children hospitalised with respiratory syncytial virus (RSV), parainfluenza virus (PIV), human metapneumovirus (hMPV) and influenza virus (IFV).

METHODS

We used a probabilistically linked population cohort born in Western Australia between 2010 and 2020 and hospitalised before the age of 2 years. Outcomes compared included length of hospital stay (LOS), admission to intensive care unit (ICU), need for respiratory support (RS), complex hospital course (RS, death, ICU admission or LOS >75th percentile), 7-day and 30-day mortality, hospital-in-the-home care, 30-day all-cause and ALRI-specific readmissions and emergency department presentations 14 days prior to hospitalisation. Logistic regression was used for binary outcomes, and negative binomial regression was used for discrete count variables. Incidence rates, time to RS and time to readmissions were calculated using survival analysis techniques.

RESULTS

The final cohort included 210 997 hospitalised children under 24 months of age for a total of 315 769 admissions. Infants hospitalised before 6 months had the highest rates for all virus-specific hospitalisations, particularly RSV hospitalisations (50.4 per 1000 child-years (95% CI 48.7 to 52.1)). Infants <6 months had higher odds of an ICU admission (adjusted OR (aOR) 2.39, 95% CI 1.36 to 4.19) and RS (aOR 4.68, 95% CI 2.95 to 7.44) and a complex hospital course (aOR 2.69, 95% CI 2.13 to 3.42) with RSV and four times higher hazards of requiring RS earlier (adjusted HR (aHR) 4.06, 95% CI 2.59 to 6.36). An ALRI-coded 30-day readmission was recorded in 10%-24% of virus-specific hospitalisations.

DISCUSSION

Young infants have a more severe and complex hospital course with RSV hospitalisation compared with hospitalisation with other respiratory viruses and should be prioritised for prevention measures such as the single-dose monoclonal antibody, nirsevimab.

Respiratory Viral Testing Rate Patterns in Young Children Attending Tertiary Care Across Western Australia: A Population-Based Birth Cohort Study

BACKGROUND

An understanding of viral testing rates is crucial to accurately estimate the pathogen-specific hospitalisation burden. We aimed to estimate the patterns of testing for respiratory syncytial virus (RSV), influenza virus, parainfluenza virus (PIV) and human metapneumovirus (hMPV) by geographical location, age and time in children <5 years old in Western Australia.

METHODS

We conducted a population-based cohort study of children born between 1 January 2010 and 31 December 2021, utilising linked administrative data incorporating birth and death records, hospitalisations and respiratory viral surveillance testing records from state-wide public pathology data. We examined within-hospital testing rates using survival analysis techniques and identified independent predictors of testing using binary logistic regression.

RESULTS

Our dataset included 46,553 laboratory tests for RSV, influenza, PIV, or hMPV from 355,021 children (52.5% male). Testing rates declined in the metropolitan region over the study period (RSV testing in infants: from 242.11/1000 child-years in 2012 to 155.47/1000 child-years in 2018) and increased thereafter. Conversely, rates increased in non-metropolitan areas (e.g., RSV in Goldfields: from 364.92 in 2012 to 504.37/1000 child-years in 2021). The strongest predictors of testing were age <12 months (adjusted odds ratio [aOR] = 2.25, 95% CI 2.20-2.31), preterm birth (<32 weeks: aOR = 2.90, 95% CI 2.76-3.05) and remote residence (aOR = 0.77, 95% CI 0.73-0.81).

CONCLUSION

These current testing rates highlight the potential underestimation of respiratory virus hospitalisations by routine surveillance and the need for estimation of the true burden of respiratory virus admissions.