RSV prophylaxis use in high-risk infants in Western Australia, 2002-2013: a record linkage cohort study

Background

The monoclonal antibody, palivizumab is licensed for use in high-risk infants to prevent severe illness caused by respiratory syncytial virus (RSV). The level of its use and compliance with current jurisdictional guidelines which were amended in 2010, is unknown. We determined the level of palivizumab use in a cohort of high-risk infants in Western Australia.

Methods

Using probabilistically linked administrative data, we conducted a birth cohort study within tertiary neonatal intensive care units (NICUs) born between 2002 and 2013. We described palivizumab use by patient characteristics, eligibility criteria according to guidelines over the period of study and identified predictors of its use.

Results

Of 24,329 infants admitted to tertiary NICUs, 271 (1.1%) were dispensed 744 palivizumab doses with 62.5% being dispensed to infants born 2010–2013. The median number of doses received was 2. A total of 2679 infants met at least one of three criteria for palivizumab (criteria 1: gestational age at birth < 28 weeks and chronic lung disease; criteria 2: gestational age < 28 weeks and Aboriginal; criteria 3: congenital heart disease not otherwise in criteria 1 or 2). The extent of palivizumab use differed across the 3 groups. Of 803 infants meeting criteria 1, 21.8% received at least 1 dose of palivizumab; 52.8% from 2010 onwards. From 174 infants meeting criteria 2, 14.4% received at least 1 dose; 43.1% from 2010 onwards and from 1804 births meeting criteria 3, only 3.7% received at least 1 dose; 5.4% from year of birth 2010 onwards). In adjusted analyses, being born after 2010, being extreme preterm, chronic lung disease, congenital lung disease and being born in autumn or winter were independent predictors of palivizumab use.

Conclusion

In this high-risk setting and notwithstanding the limitations of our data sources, the level of compliance of palivizumab use against current guidelines was low. Most doses were dispensed to infants meeting at least one high-risk criterion. Evidence of incomplete dosing is an important finding in light of recent developments of single dose monoclonal antibodies offering longer protection.

RSV prophylaxis use in high-risk infants in Western Australia, 2002-2013: a record linkage cohort study

BACKGROUND

The monoclonal antibody, palivizumab is licensed for use in high-risk infants to prevent severe illness caused by respiratory syncytial virus (RSV). The level of its use and compliance with current jurisdictional guidelines which were amended in 2010, is unknown. We determined the level of palivizumab use in a cohort of high-risk infants in Western Australia.

METHODS

Using probabilistically linked administrative data, we conducted a birth cohort study within tertiary neonatal intensive care units (NICUs) born between 2002 and 2013. We described palivizumab use by patient characteristics, eligibility criteria according to guidelines over the period of study and identified predictors of its use.

RESULTS

Of 24,329 infants admitted to tertiary NICUs, 271 (1.1%) were dispensed 744 palivizumab doses with 62.5% being dispensed to infants born 2010-2013. The median number of doses received was 2. A total of 2679 infants met at least one of three criteria for palivizumab (criteria 1: gestational age at birth < 28 weeks and chronic lung disease; criteria 2: gestational age < 28 weeks and Aboriginal; criteria 3: congenital heart disease not otherwise in criteria 1 or 2). The extent of palivizumab use differed across the 3 groups. Of 803 infants meeting criteria 1, 21.8% received at least 1 dose of palivizumab; 52.8% from 2010 onwards. From 174 infants meeting criteria 2, 14.4% received at least 1 dose; 43.1% from 2010 onwards and from 1804 births meeting criteria 3, only 3.7% received at least 1 dose; 5.4% from year of birth 2010 onwards). In adjusted analyses, being born after 2010, being extreme preterm, chronic lung disease, congenital lung disease and being born in autumn or winter were independent predictors of palivizumab use.

CONCLUSION

In this high-risk setting and notwithstanding the limitations of our data sources, the level of compliance of palivizumab use against current guidelines was low. Most doses were dispensed to infants meeting at least one high-risk criterion. Evidence of incomplete dosing is an important finding in light of recent developments of single dose monoclonal antibodies offering longer protection.

Influence of weather on incidence of bronchiolitis in Australia and New Zealand

AIM

We aimed to examine the impact of weather on hospital admissions with bronchiolitis in Australia and New Zealand.

METHODS

We collected data for inpatient admissions of infants aged 2-12 months to seven hospitals in four cities in Australia and New Zealand from 2009 until 2011. Correlation of hospital admissions with minimum daily temperature, wind speed, relative humidity and rainfall was examined using linear, Poisson and negative binomial regression analyses as well as general estimated equation models. To account for possible lag between exposure to weather and admission to hospital, analyses were conducted for time lags of 0-4 weeks.

RESULTS

During the study period, 3876 patients were admitted to the study hospitals. Hospital admissions showed strong seasonality with peaks in wintertime, onset in autumn and offset in spring. The onset of peak incidence was preceded by a drop in temperature. Minimum temperature was inversely correlated with hospital admissions, whereas wind speed was directly correlated. These correlations were sustained for time lags of up to 4 weeks. Standardised correlation coefficients ranged from -0.14 to -0.54 for minimum temperature and from 0.18 to 0.39 for wind speed. Relative humidity and rainfall showed no correlation with hospital admissions in our study.

CONCLUSION

A decrease in temperature and increasing wind speed are associated with increasing incidence of bronchiolitis hospital admissions in Australia and New Zealand.

Time series analysis of RSV and bronchiolitis seasonality in temperate and tropical Western Australia

Respiratory syncytial virus (RSV) causes respiratory illness in young children and is most commonly associated with bronchiolitis. RSV typically occurs as annual or biennial winter epidemics in temperate regions, with less pronounced seasonality in the tropics. We sought to characterise and compare the seasonality of RSV and bronchiolitis in temperate and tropical Western Australia. We examined over 13 years of RSV laboratory identifications and bronchiolitis hospitalisations in children, using an extensive linked dataset from Western Australia. We applied mathematical time series analyses to identify the dominant seasonal cycle, and changes in epidemic size and timing over this period. Both the RSV and bronchiolitis data showed clear winter epidemic peaks in July or August in the southern Western Australia regions, but less identifiable seasonality in the northern regions. Use of complex demodulation proved very effective at comparing disease epidemics. The timing of RSV and bronchiolitis epidemics coincided well, but the size of the epidemics differed, with more consistent peak sizes for bronchiolitis than for RSV. Our results show that bronchiolitis hospitalisations are a reasonable proxy for the timing of RSV detections, but may not fully capture the magnitude of RSV epidemics.

Morbidity due to acute lower respiratory infection in children with birth defects: a total population-based linked data study

BACKGROUND

Acute lower respiratory infections (ALRIs) are leading causes of hospitalisation in children. Birth defects occur in 5% of live births in Western Australia (WA). The association between birth defects and ALRI hospitalisation is unknown.

METHODS

We conducted a retrospective cohort study of 245,249 singleton births in WA (1996-2005). Population-based hospitalisation data were linked to the WA Register of Developmental Anomalies to investigate ALRI hospitalisations in children with and without birth defects. We used negative binomial regression to estimate associations between birth defects and number of ALRI hospitalisations before age 2 years, adjusting for known risk factors.

RESULTS

Overall, 9% of non-Aboriginal children and 37% of Aboriginal children with birth defects had at least one ALRI admission before age 2 years. Aboriginal children (IRR 2.3, 95% CI: 1.9-2.8) and non-Aboriginal children (IRR 2.0, 95% CI: 1.8-2.2) with birth defects had higher rates of hospitalisation for an ALRI than children with no birth defects. Rates of ALRI hospitalisation varied by type of defect but were increased for all major birth defects categories, the highest rate being for children with Down syndrome (IRR 8.0, 95% CI: 5.6-11.5). The rate of ALRI hospitalisation was 3 times greater in children with multiple birth defects than in those with isolated defects.

CONCLUSIONS

Children with birth defects experience higher rates of hospitalisation for ALRIs before age 2 years than children with no birth defects. Optimal vaccination coverage and immunoprophylaxis for specific categories of birth defects would assist in reducing hospitalisation rates for ALRI.

Can linked emergency department data help assess the out-of-hospital burden of acute lower respiratory infections? A population-based cohort study

Background

There is a lack of data on the out-of-hospital burden of acute lower respiratory infections (ALRI) in developed countries. Administrative datasets from emergency departments (ED) may assist in addressing this.

Methods

We undertook a retrospective population-based study of ED presentations for respiratory-related reasons linked to birth data from 245,249 singleton live births in Western Australia. ED presentation rates <9 years of age were calculated for different diagnoses and predictors of ED presentation <5 years were assessed by multiple logistic regression.

Results

ED data from metropolitan WA, representing 178,810 births were available for analysis. From 35,136 presentations, 18,582 (52.9%) had an International Classification of Diseases (ICD) code for ALRI and 434 had a symptom code directly relating to an ALRI ICD code. A further 9600 presentations had a non-specific diagnosis. From the combined 19,016 ALRI presentations, the highest rates were in non-Aboriginal children aged 6–11 months (81.1/1000 child-years) and Aboriginal children aged 1–5 months (314.8/1000). Croup and bronchiolitis accounted for the majority of ALRI ED presentations. Of Aboriginal births, 14.2% presented at least once to ED before age 5 years compared to 6.5% of non-Aboriginal births. Male sex and maternal age <20 years for Aboriginal children and 20–29 years for non-Aboriginal children were the strongest predictors of presentation to ED with ALRI.

Conclusions

ED data can give an insight into the out-of-hospital burden of ALRI. Presentation rates to ED for ALRI were high, but are minimum estimates due to current limitations of the ED datasets. Recommendations for improvement of these data are provided. Despite these limitations, ALRI, in particular bronchiolitis and croup are important causes of presentation to paediatric EDs.