Incidence and seasonality of respiratory syncytial virus hospitalisations in young children in Denmark, 2010 to 2015

Abstract

For future decisions on respiratory syncytial virus (RSV)-vaccination strategies and implementation into national immunisation-programmes, we used national registry data (hospitalisation, microbiology and vital statistics) to determine the age-specific incidence and direct medical costs of annual RSV-associated admissions in children < 5 years-old for the period of 2010–2015. We identified ca 2,500 RSV-associated hospitalisations annually amounting to total direct medical-costs of ca EUR 4.1 million per year. The incidence of RSV-associated hospitalisations peaked in infants 1–2 months of age followed by infants 2–3 months of age, and infants < 1 month of age, respectively. Infant boys were at higher risk of severe RSV infection as compared to infant girls: male-to-female ratio peaked with 1.4 at four months of age and gradually levelled out with increasing age to 1.0 at 4 years of age. Five RSV-associated deaths were identified. Our findings demonstrate that in a western country as Denmark, RSV constitutes a considerable burden on childhood health. Furthermore, the best approach to reduce the high incidence of RSV-associated hospitalisations in young infants < 3 months of age may be maternal vaccination due to general challenges in achieving sufficient and protective immune responses in young infants.

Respiratory syncytial virus‐associated hospitalisations in Australia, 2006–2015

“…Most RSV‐associated hospitalisations are of children under 6 months of age; published rate estimates range from 1700 to 4590 per 100 000 population, depending on the study population and methodology . It has been reported that there are more RSV‐associated hospitalisations of young Australian children than influenza‐associated hospitalisations .…”

“…The main limitation of our study was that we estimated RSV‐associated hospitalisation rates on the basis of RSV‐specific ICD codes, an approach that can underestimate the pathogen‐specific disease burden of respiratory infections . Diagnostic codes other than RSV‐specific codes have also been assigned to RSV‐associated hospitalisations .…”

“…We extracted hospitalisations with International Classification of Diseases, tenth revision, Australian modification (ICD‐10‐AM) diagnosis codes for RSV pneumonia (J12.1), RSV bronchitis (J20.5), RSV bronchiolitis (J21.0), and RSV as the cause of diseases classified to other chapters (RSV organism) (B97.4). These codes were selected on the basis of earlier studies and expert opinion. Hospitalisations of children under 24 months of age with a principal diagnosis code of unspecified acute bronchiolitis (J21.9) were also extracted, as this diagnosis is frequently associated with RSV disease .…”

“…7,[13][14][15]24,28 Diagnostic codes other than RSVspecific codes have also been assigned to RSV-associated hospitalisations. 7,13,15 We found that the seasonal patterns of hospitalisations for conditions coded as unspecified acute bronchiolitis were similar to those of RSV bronchiolitis, which suggests the involvement of RSV as a pathogen in bronchiolitis may be under-ascertained. RSV is detected in 50-70% of young children hospitalised for bronchiolitis, but other pathogens, including parainfluenza viruses, human metapneumovirus and influenza viruses, are also associated with this diagnosis.…”

Change in respiratory syncytial virus seasonality in Finland

“…Interestingly, in Nordic countries, biennial epidemiological pattern is typical with a large epidemic every 2 years alternating with a minor one. This kind of biennial seasonality has been reported, in addition to Nordic countries, in Croatia and Germany …”