Influenza is an ongoing issue in Australia leading to significant morbidity and mortality, particularly in the elderly. Disease severity and vaccination are crucial in understanding the spread and burden of influenza, while many other viral pathogens also contribute to the burden of respiratory disease. There is emerging evidence that exposure to one infection may provide individuals with broad – but short-lived – protection to other respiratory infections, and that influenza vaccination can interfere with this immunity. This project identifies population level consequences of disease severity, vaccination and virus interference in collaboration with Prof Heath Kelly, Dr James Fielding (Victorian Infectious Disease Reference Laboratory), and Dr Hannah Moore (Telethon Children’s Institute).