Creating a birth cohort to examine RSV bronchiolitis hospital
admission rates among term and preterm infants in England
Joanna Murray 1, Alex Bottle 1, Mike Sharland 2, Neena Modi 3, Paul Aylin 1, Azeem Majeed 1 and Sonia Saxena1
1
Department of Primary Care and Public Health, Imperial College London, UK
2 Paediatric Infectious Diseases Unit, St George’s Hospital NHS Trust, London, UK
3 Section of Neonatal Medicine, Department of Medicine, Imperial College London
On behalf of the Medicines for Neonates Investigator Group: Neena
Modi, Peter Brocklehurst, Jane Abbott, Kate Costeloe, Elizabeth Draper,
Azeem Majeed, Jacquie Kemp, Deborah Ashby, Alys Young, Stavros Petrou
Results
All bronchiolitis admissions
Introduction
• Bronchiolitis is a common respiratory illness among infants, typically caused
by respiratory syncytial virus (RSV). It is usually a mild, self-limiting illness
but in some infants may be more severe, requiring hospital admission.1
Birth cohort (n=296618)
7189 admissions to hospital with bronchiolitis during the first year of life
• Infants known to be at high risk of severe RSV infection include those with
chronic lung disease, congenital heart disease, immunodeficiency, low birth
weight and those born preterm (around 8% of newborns in the UK).2-5
• Evidence from the US suggests many infants admitted to hospital with RSV
infection are healthy, with no risk factors for severe RSV infection.3
• To date, no national studies have reported the disease burden at a
population level in the UK.
• An active immunisation against RSV is currently in phase III trials.
24.2 admissions per 1000 infants under 1 year (95% CI 23.7 to 24.8)
Median age at admission = 120 days (Inter-quartile range = 61 to 209)
Figure 1. Age at bronchiolitis admission
900
800
700
RSV Bronchiolitis
600
Number of
500
hospital
admissions 400
Unspecified Bronchiolitis
300
Aim
200
We aimed to examine RSV bronchiolitis hospital
admission rates among term and preterm infants
in England.
100
0
0
1
2
3
4
5
6
7
8
9
Age at admission (in months)
10
11
12
Bronchiolitis admissions among term and preterm infants
Among infants who had a bronchiolitis admission:
15% were born preterm (n =1050)
47.3 per 1000 infants (95%CI 44.4 to 50.2)
Methods
We developed a population-based birth cohort with follow-up to age 1 year
using the Hospital Episode Statistics (HES) database.
We identified individual birth records from a twelve month period (01/04/2007
to 31/03/2008), from 71 NHS hospitals across England (where >90% of their
birth records contained complete recording of key variables, birth weight and
gestational age) and linked to subsequent hospital admission records.
85% were born at term (n = 6139)
22.4 per 1000 infants (95%CI 21.8 to 22.9)
Age
Median age at bronchiolitis admission among infants born:
Preterm = 136 days (IQR = 71 to 221)
P < 0.001
Term = 118 days (IQR = 59 to 207)
Infants were considered preterm if their gestational age at birth was less than
37 weeks, in accordance with the WHO definition of premature birth.
Length of stay
Median length of stay for a bronchiolitis admission among infants born:
We identified emergency admissions with a primary diagnosis of bronchiolitis
using the ‘J21’ ICD-10 codes. Most bronchiolitis admissions were coded with
unspecific aetiology and around a third were coded as being due to RSV.
Preterm = 1 day (IQR = 0 to 3)
No difference
Term = 1 day (IQR = 0 to 3)
We calculated bronchiolitis hospital admission rates among term and preterm
born infants. We also examined age at bronchiolitis admission and the median
length of stay for admissions, as a proxy measure of severity of illness.
Conclusions
85% of infants admitted to hospital with bronchiolitis in England are born
at term and many are admitted for just 1 day.
The peak in RSV bronchiolitis admissions at age 1 month is earlier than
previously reported in other developed countries.
These findings have important implications for both active and passive
immunisation policies.
Acknowledgements
References
We wish to thank the National Institute for Health Research (NIHR) “Medicines for Neonates” Programme Grant for Applied Research which provided the
main source of funding for this study (Principal Investigator Professor Neena Modi, Imperial College London). We also thank Dr Paul Aylin and the Dr Foster
Unit at Imperial College London for providing access to the Hospital Episode Statistics database.
1. Papadopoulos NG, Moustaki M, Tsolia M, Bossios A, Astra E, Prezerakou A et al. Association of Rhinovirus Infection with Increased Disease
Severity in Acute Bronchiolitis. Am J Respir Crit Care Med 2002; 165(9):1285-1289.
2. Smyth RL, Openshaw PJ. Bronchiolitis. The Lancet 2006; 368(9532):312-322.
3. Hall CB, Weinberg GA, Iwane MK, Blumkin AK, Edwards KM, Staat MA et al. The Burden of Respiratory Syncytial Virus Infection in Young Children.
The New England Journal of Medicine 2009; 360(6):588-598.
4. Hall CB. Respiratory syncytial virus in young children. The Lancet 2010; 375(9725):1500-1502.
5. Office for National Statistics. News Release: 1 in 13 live births in England and Wales are born preterm.
http://www.statistics.gov.uk/pdfdir/preterm0507.pdf
This publication presents independent research commissioned by the National Institute for Health Research (NIHR) under its Programme Grants for Applied
Research scheme (RP-PG-0707-10010). The views expressed in this publication are those of the authors and not necessarily those of the NHS, the NIHR or
the Department of Health. The funders had no role in the study design, collection, analysis, and interpretation of data, in the writing of the report or in the
decision to submit the paper for publication.
Email address: joanna.murray@imperial.ac.uk