National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases New Childrens Hospital, Westmead

This paper evaluates the data describing respiratory syncytial virus (RSV) infection in infants and children aged less than five years in NSW, and in particular children aged less than one year. This younger age group forms the primary target group for immunisation against RSV and vaccine development is now well advanced. The data outlined in this paper provide a baseline for evaluating the burden of disease before and after the introduction of a vaccine. BACKGROUND RSV is the most important cause of viral lower respiratory tract disease in infants and children throughout the world.1 RSV is estimated to cause up to 80 per cent of hospital admissions for bronchiolitis in infants under one year of age and is characterised by wheezing and hypoxia. RSV is also associated with pneumonia, croup, bronchitis, otitis media and upper respiratory tract infections.2,3,4 Acute bronchiolitis and bronchitis are the sixth most common causes of hospital admissions in Australian children.5 Overseas literature suggests that infants aged 2–6 months are most severely affected by RSV infection, and mortality rates are higher among those with underlying respiratory and cardiac conditions.2,6 Despite the considerable effect on public health of this disease, there are very little recent epidemiological data available in Australia. Treatment options remain limited but vaccine development is proceeding and clinical trials have commenced.7 METHODS As RSV infection is not a notifiable disease, a number of sources of data were used to build a picture of the age distribution, seasonality and incidence of RSV infection in NSW. Three data sources, each identifying the most severe outcomes of RSV disease (that is, cases resulting in hospitalisation) were used