Acute Lower Respiratory Infections Among Indigenous Children in the Northern Territory of Australia: A Decade of Observation Spanning Three Generations of Pneumococcal Conjugate Vaccine

Abstract

Background:­­­­ For Indigenous infants living in Australia’s Northern Territory (NT) acute lower respiratory infections (ALRIs) are a leading cause of hospitalisation and preventable mortality. The study describes the burden of ALRI hospitalisation in this population from 2006 to 2015 with contrast between three periods of different pneumococcal conjugate vaccine (PCV) use. Methods: We conducted a historical cohort study of NT Indigenous infants born between 1st January 2006 and 31st December 2015 and followed until age 12 months. Data were from administrative hospital and perinatal datasets. International classification of diseases codes were used to identify respiratory hospitalisations of interest: all cause ALRI, all cause pneumonia, bacterial pneumonia, viral pneumonia, influenza-like illness (ILI), respiratory syncytial virus ALRI (RSV-ALRI) and pneumococcal ALRI. Incidence rates were compared between PCV eras (7-valent PCV-PCV7, 2006-2009; PCV10, 2009-2011; PCV13, 2011-2015) using interrupted time trend analysis and negative binomial regression. Findings: Over the study period 4138 ALRI episodes (31% of all hospitalisations) occurred among 2888 of the 14594 infants (20% of the cohort). The overall ALRI hospitalisation rate was 29.7 episodes per 100 child-years. Prominent risk factors associated with ALRI hospitalisation were living in a remote community or the Central desert region, being born preterm or with low birth weight. ALRI rates were lowest in the PCV13 era in association with a significant reduction in bacterial pneumonia hospitalisations in the PCV13 relative to the PCV10 (IRR 0∙68, 95% CI 0∙57-0∙81) and PCV7 (IRR 0∙70, 95% CI 0∙60-0∙81) eras. In contrast, RSV-ALRI rates were 4∙9 episodes per 100 child-years in each era. Interpretation: We found a 30% reduction in bacterial-coded pneumonia hospitalisation episodes during the era of PCV13 use. Despite this, one in five NT Indigenous infants continue to be hospitalised with an ALRI in their first year of life. RSV associated ALRI rates were high and remained unchanged over a decade. Funding Statement: This work was supported by the National Health and Medical Research Council (NHMRC) of Australia. MJB was funded by an NHMRC Early Career Fellowship (1088733) and NHMRC-funded `Hot North - Improving Health Outcomes in the Tropical North’ Fellowship (1131932). JB is supported by a NHMRC scholarship (1150901) and a NHMRC-funded Centre of Research Excellence in Ear and Hearing Health of Aboriginal and Torres Strait Islander children scholarship (1078557). VMO none. SJP was supported by a NHMRC Peter Doherty Early Career Fellowship (1113302). AJL was supported by NHMRC Fellowship (1020561), the NHMRC-funded Centre of Research Excellence in Ear and Hearing Health of Aboriginal and Torres Strait Islander Children (1078557), The Balnaves Foundation, the Northern Territory Government and the Australian Government. PSM none. RMA none. LM was supported by an Australian Postgraduate Award through Charles Darwin University and an Enhanced Living scholarship through Menzies School of Health Research towards a Doctor of Philosophy degree. RW none. ABC is supported by Australia’s NHMRC Practitioner Fellowship (1058213) and a Children’s Hospital Foundation Fellowship, Queensland (50286). Declaration of Interests: The authors stated: None exist. Ethics Approval Statement: This project was approved by the Human Research Ethics Committee of the NT Department of Health and Menzies School of Health Research (HREC 2015-2406).